Top growth is yellowing heavily, what's the cause?

[AgedMaster]

Plants turn yellowish at the top when they first enter flower.
In fact, you can kind of use it as an indicator that they've started flowering even before pistils form.
Cheers.

This happened to me a couple grows ago the plant ended up fine all the green came back i just fed the same as i was until it got greener then increased EC slightly just don't do anything drastic .it was a wild auto 8ft plus its also happened one other time but I don't have a pic it happened with autos both times

 

[SmokingWings]

For most soils the pH of the nutes should be in the 6.3 area. Pro Mix & Bio Bizz I think are different, but not sure.
@SmokingWings probably knows.

According to BioBuzz a PH of 6.2-6.3 (I had to look it up).

Usually what I do, too. Just look it up, starting with the web site for the manufacturer of the soil or soil-less mix. Then I sometimes take a look at what other growers are saying about the companies product by following some of the other links that popped up when I hit "Enter" after typing in my search question.

Some of the companies are building mixes based on peat moss or coco coir or sometimes a combination and the first thought is to pH the water like the mix is for a hydro situation. But, now-a-days they are adding other materials to the mix so the lower pH is not recommended and the grower has to go with something closer to what would be used in a natural or mineral soil.

 

[SmokingWings]

Yesterday I gave the first flowering feeding, including TopMax, Bloom, Grow & CalMag, normal recommended dose for autoflowers. pH still at around 6.8, PPFD at 590-620. This problem appeared around 5 or 6 days ago. I have some hope that it was just some kind of deficiency, as I only fed it half a dose of Fishmix until now, because the Allmix was rather hot by itself.

Gonna throw a bit of monkey-wrench into the discussion. I am wondering if it is actually a case of excess and not a deficiency.

If the pen is working even half-way decent and the pH is even close to that very high reading of 6.8 then is it possible that the plant is able to get the maximum, or close, of the available Nitrogen, Phosphorous, and Potassium along with Calcium and Magnesium. What it would have a hard time picking up would be Manganese and Iron. We would need to look up the nutrient ratios in the fertilizer mixes mentioned.

Using the Jorge Cervantes "Excess and Deficiency" chart and the 420Magazine pH Chart it does look like the yellowing in the new growth shown in the photographs there could be an excess of P and K both of which show up at the top of the plant in the newer growth.

I just ordered a high quality pH meter which will probably arrive monday or tuesday, because I don't trust the $20 one anymore. I feel like the pH is too high,

This is why it is a good idea to have a back-up system handy. Pull out a pH test kit that uses drops. Even if someone has a hard time telling the differences in the color chart included with the test kit there will be enough of a change between 6.3 and 6.8 to show up after using the drops.

 

[Acid]

So, here's a little first update - New pH tester just arrived, calibrated in 4.0 and 7.0 buffer solution, it's ready I guess.

Yesterday I pre-made two slurries (I know it wasn't recommended but I still wanted to try it for my own experience ), and did the slurry test.

Here's the result:

Right plants slurry had a pH of 6.7, left plant had a pH of 6.7 too. Is this already a good indicator for an iron deficiency, or is this bad news for whatever is going on? I'm saying this because my plants already look worse than yesterday. I wanna mention that I took soil from pretty much the middle of the pot, not the top. I tried my best to not damage lots of roots, but I wanted a precise reading. I'd rather have tiny damage but good readings, than no damage but a damaged plant in the end. It was also just a finger-sized hole, so probably not damaged much at all (hopefully).

Also did a general tap water test, pH is 7.9 which is pretty high.

Also did a nutrient mix as I always do, just as a test. Means water + the nutes. Came out to a pH of 6.8

I also wanna mention - After about an inch, the soil still feels a bit hard and wet. I watered on the 13th before the lights went out at 11pm. It's the 18th now, surrounding soil at the corners is already dry, but everything near the stem is still kinda wet after around an inch. I watered each plant with 0.3 gallons of water, or around a litre each. There's enough ventilation, tent is also half open most of the time because of temperatures, fans pointing at the main stem in the pots, I'm all out of ideas. The soil is just plain fresh BioBizz Allmix, nothing added. I thought this was fine by itself, but I feel like it may be a bit too.. thick after some waterings. But I also can't help it now I think, have to accept it. Should've followed the advice to add a layer of those brown pearls on the bottom for more aeration.

Here's my "plan": Use Biobizz pH down with all nutes and water tomorrow, to get the pH to 6.2 or 6.1 (recommended was 6.2 by someone here) for the water I use, and water as usual. Should I flush the system, or not? I've never had runoff, probably because the pots just were too big in the end. But it's also all Biobizz, soil and nutes, so I feel like I don't need any runoff. May also be worth mentioning. I expected them to grow a bit bigger, but autoflowers just do their thing.

Small edit: Noticed this single leaf looking a bit strange, too. Possible clues?

 

[AgedMaster]

Hi here is a PH availability chart 6.2 or 6.3 would be perfect don't no if u have seen this

 

[Emilya Green]

Always pH adjust your incoming fluids to 6.3 pH, right before you pour it on the plants. 6.8 is too high and explains your iron deficiency showing in your top growth. Pay no attention to your soil pH... the slurry test was in my humble opinion, a waste of your good time. Soil is set to the high end, around 6.8 pH, for a very good reason. There is no need to adjust anything there. Just pH adjust your incoming fluids to 6.3, whether it is water mixed with nutes or just plain water.

 

[Phytoplankton]

Here's my "plan": Use Biobizz pH down with all nutes and water tomorrow, to get the pH to 6.2 or 6.1 (recommended was 6.2 by someone here) for the water I use, and water as usual. Should I flush the system, or not? I've never had runoff, probably because the pots just were too big in the end. But it's also all Biobizz, soil and nutes, so I feel like I don't need any runoff. May also be worth mentioning. I expected them to grow a bit bigger, but autoflowers just do their thing.

Good plan, I suggest reading @Emilya Green write up on how to water a potted plant. The Proper Way To Water A Potted Plant

 

[Acid]

Always pH adjust your incoming fluids to 6.3 pH, right before you pour it on the plants. 6.8 is too high and explains your iron deficiency showing in your top growth. Pay no attention to your soil pH... the slurry test was in my humble opinion, a waste of your good time. Soil is set to the high end, around 6.8 pH, for a very good reason. There is no need to adjust anything there. Just pH adjust your incoming fluids to 6.3, whether it is water mixed with nutes or just plain water.

Haha, it may have been a waste, but I felt better after doing it. Thanks a lot for confirming my next step, I'll pH the next watering accordingly and hope for the best.

 

[Sueet]

The markings on that single leaf kind of look like early thrip damage to me.

 

[Acid]

So before opening a new thread, here's my problem right now - For any info, temps and everything are the same as in the first post. The apparent iron deficiency didn't get any better so far, I don't know if it'll go away after fixing the pH though. Yes I did fix it already, 2 days ago. pH should be at around 6.3 now.

Right now, this is what's happening REALLY fast to lots of leaves. I'm scared and don't know what to do. What's happening here?

 

[Emilya Green]

Looks like maybe a magnesium deficiency... what are you feeding your plant and is it a full dosage? Are you giving any calmag?

 

[Acid]

Looks like maybe a magnesium deficiency... what are you feeding your plant and is it a full dosage? Are you giving any calmag?

I only have the Biobizz line, last feeding was 2ml grow, 2ml bloom, 2ml topmax, and 0.3ml of calmag in 2L of tapwater. There were lots of dry pockets in the soil, so this time I gave a bigger amount of water. It's 25L pots with around 20L of soil. PH down was also added until the nutrient water was at around 6.2

I read that mag deficiencies can appear in connection to an iron deficiency, can this be a late symptom because my iron deficiency was already on full destruction mode?

 

[Emilya Green]

I only have the Biobizz line, last feeding was 2ml grow, 2ml bloom, 2ml topmax, and 0.3ml of calmag in 2L of tapwater. There were lots of dry pockets in the soil, so this time I gave a bigger amount of water. It's 25L pots with around 20L of soil. PH down was also added until the nutrient water was at around 6.2

I read that mag deficiencies can appear in connection to an iron deficiency, can this be a late symptom because my iron deficiency was already on full destruction mode?

I don't run that line. Is that the recommended dose or have you adjusted? I question that because pH up is usually needed after adding nutrients and you say you added pH down. You've got me scratching my head over here in confusion.

 

[Roy Growin]

Dosage is way too low - at this stage you should be giving something like 2ml Gro, 4ml Bloom, 1ml CaMg per Litre
You're currently providing 1ml/L Grow & Bloom and 0.15ml/L of CaMg
I generally used 2-4ml of each start to finish

 

[SmokingWings]

There were lots of dry pockets in the soil, so this time I gave a bigger amount of water.

If the soil became over dry it will resist soaking up the water. To fix it takes a bit more than just giving more water if that extra water is just going to run right through or around the dry pockets.

Give the plant a small amount of water and let that slowly soak into the soil. Then come back in 20 to 30 minutes and give another small amount and again in another 20-30 minutes. At first if you notice water coming out the bottom drain holes it meant too much water at one time. Slow down and smaller amounts will go a long way to getting the dry areas taken care of.

 

[Roy Growin]

I don't run that line. Is that the recommended dose or have you adjusted? I question that because pH up is usually needed after adding nutrients and you say you added pH down. You've got me scratching my head over here in confusion.

BB is slightly acidic so 3ml/L drops the pH of tap water by around 0.5 point so usually needs a bit of adjustment

 

[Acid]

I don't run that line. Is that the recommended dose or have you adjusted? I question that because pH up is usually needed after adding nutrients and you say you added pH down. You've got me scratching my head over here in confusion.

My pH after adding nutrients to the water is at 6.8, as my tapwater has a pH of 7.9-8, which is pretty high. So I add a pH down, to get to around 6.2-6.3 of ph'ed water with nutrients. Biobizz recommends a pH of 6.3 or something like that, as I also use the allmix soil.

I don't know how to reply to all comments at once, so I'll just do it here. I felt like giving a bigger amount of nutrients is wrong, as my plants (two autoflowers) don't seem to be that big anyways. They're rather tiny, as they took a few hits here and there. Should I still add more?

 

[Roy Growin]

My pH after adding nutrients to the water is at 6.8, as my tapwater has a pH of 7.9-8, which is pretty high. So I add a pH down, to get to around 6.2-6.3 of ph'ed water with nutrients. Biobizz recommends a pH of 6.3 or something like that, as I also use the allmix soil.

I don't know how to reply to all comments at once, so I'll just do it here. I felt like giving a bigger amount of nutrients is wrong, as my plants (two autoflowers) don't seem to be that big anyways. They're rather tiny, as they took a few hits here and there. Should I still add more?

https://www.biobizz.com/wp-content/uploads/2020/03/Nutrient-Schedule-EN-2020.pdf

 

[Emilya Green]

My pH after adding nutrients to the water is at 6.8, as my tapwater has a pH of 7.9-8, which is pretty high. So I add a pH down, to get to around 6.2-6.3 of ph'ed water with nutrients. Biobizz recommends a pH of 6.3 or something like that, as I also use the allmix soil.

I don't know how to reply to all comments at once, so I'll just do it here. I felt like giving a bigger amount of nutrients is wrong, as my plants (two autoflowers) don't seem to be that big anyways. They're rather tiny, as they took a few hits here and there. Should I still add more?

So what you were saying is that your feelings are what is hurting your plants. There should be no distinction between autos or photos, just follow the directions the nutrient manufacturer gives you and stop second guessing the experts who designed the stuff. If they thought you should feed autos differently they would have given you a separate nutrient plan just for them.

 

[SmokingWings]

...as I also use the allmix soil.
.........
They're rather tiny, as they took a few hits here and there. Should I still add more?

Keep in mind that BioBizz All-Mix is not a mineral, natural or traditional soil mix. All-Mix might be 100% organic but out of that 100% it is 55% Peat Moss which is rather inert in that it will supply very, very little nutrients on its own until the peat decomposes several years down the road and even then it is a low amount. And it is 30% Perlite which is also inert but takes care of the aeration and some water retention.

That leaves 10% which is worm manure (worm castings) and 5% for the "BioBizz Pre-Mix" which is a natural fertilizer some of which is a rock meal which is probably water insoluble and therefore slow release.

And that is why the two plants are looking rather tiny. They just are not getting the right amounts of the nutrients they need on a continuous basis. Mix in the right amounts of Grow, Bloom, TopMax and Cal-Mag with the water and their color and overall condition should start to improve after a week or so.

There is nothing wrong with the BioBizz All-Mix"soil" but it is not a soil as most of us think of natural soils. It is a "soil-less mix" that will show what it can do once the fertilizers, in the right amounts, are added.