Edges of leaves turning brown, week 8 of flower: Need advice

[StickyDigits]

My plants are in week 8 of flower and one of the plants has brown areas on some leaves. This has been progressing over the last week or so. I would like some ideas as to what this is and how to fix it.

Start Date 2-10-19
Strain Gorilla Glue
Pot Size 5 Gallon
Medium FF Ocean Forest
Lights SP-250 LEDs
Nutes FF Trio

Watering is every 2 to 3 days. Water pH has been adjusted to 6.3-6.8. They get nutes every other watering.
The lights have been in the recommended range of 12 to 18 inches. Conditions have been about 80F and 50%RH. I have recently added an AC to send cool air into tent. The other 4 plants do not show the leaf browning to this extent. There is plenty of air flow and circulation in the tent.

 

[Chris Scorpio]

What % of nutes ya using

FF trio is a pretty hot mix, I've used it, I always ran it at half strength

 

[Emilya Green]

I always ran my Fox Farms trio and the solubles at full strength, and got amazing results from it. Your other plants are showing this to be true but in this problem plant you have found one who is a calcium hog. Since you are in the 8th week of flower, there is not much you can do at this point to have avoided this... mid flower, when you were throwing the kitchen sink at the plants per FF instructions, a little bit more calmag could have kept this from happening. Right now, you are about to finish and no harm is going to be done if you are close to the end. If this is a long running variety, and you are still several weeks away from the end, I would add more calmag to keep this from getting worse. If you are in the last two weeks, just continue on, and this plant just wont finish as pretty as the others.

 

[StickyDigits]

Thanks so much for the comments.
I have been running FF nutes at 50% until the last couple of feedings when I have upped it to near full strength, every other watering. And I have started adding the Cha Ching, Boomerang, Bembe, Microbe Brew per the chart. And I have stopped the (high Nitrogen) Grow Big. I failed to mention that I did add Dolomite Lime to the soil in the beginning for pH buffering.
This morning I added Cal Mag to their water based on my own diagnosis (thanks to this site and others). I added the Cal Mag to only two of the plants because this is my first grow and I don't want to hurt them all if I make a wrong diagnosis.
I do inspect the Trichomes every day to see if they are getting cloudy.
I have not experienced Cannabis in 40 years, but I do recall that I liked it.

 

[Emilya Green]

have not experienced Cannabis in 40 years, but I do recall that I liked it.

A couple more comments... Dolomite is primarily used as an upper buffer, so that low pH inputs are normalized into the soil range and so that there is an upward drift after watering. FFOF already had enough of this to cause a strong upward drift... you have made it faster.
This means that it is even more important to come in at the low end of the soil range, ie 6.2-6.3 so that this strong enhanced upward drift takes the pH through the entire 6.2-6.8 range between waterings. Magnesium especially is not as mobile at the top end where you have adjusted to, but more importantly is that FFOF is known for a molybdenum deficiency in late flower if you don't adjust to the low end a few times from mid flower on.
I ran FFOF and their nutes for several years a while back... and I learned a few tricks as to how to make that system work correctly. Flushing when advised is important, and following the feeding schedule is even more important.
Regarding being afraid to hurt the plants with calmag... if you are following the directions, even the heavy feeding, it would be hard to hurt these calcium and magnesium hungry plants. I see this deficiency so often that beginning late veg, I give a maintenance dosage of calmag each watering, whether they are showing symptoms or not.

 

[StickyDigits]

Thanks for those comments about FFOF @Emilya.
So if I use FFOF on the next grow I will not add the Lime.
And I have not been doing the flushes. I just water to run off on every other watering. But I do have Sledge Hammer, so I will add that to the water next time and water to run off. Then I will feed with nutes on next feeding. Then I should be about a week to harvest, so probably only pH adjusted water that last week.

 

[Emilya Green]

watering to runoff, unless you are running off a gallon of water, is not flushing. A proper flush is 3x the container size in water, with or without Sledge Hammer. The FF system uses flushes to not only clear out the last stages of nutes and gets rid of the last mix, but also to cleanse the soil of the salts that build up as the nutes break down. Watering to runoff does not cleanse the soil of this debris, even at 20%. I doubt you are anywhere near even 20% with your runoff... that would be 1 gallon per plant.
The main thing that the flush does is to allow for more uptake by getting rid of the accumulating salts that restrict the roots ability to uptake water. More uptake means bigger buds. More uptake means you can give even more nutes, again giving you bigger buds. I used to flush my FF grows 4 times.... at the end of veg, end of open sesame, at the end of beasty blooms and at the beginning of final bud swell in the last 2 weeks. When I started flushing properly, I increased my yield by about 30%.

 

[StickyDigits]

So for a 5 gallon pot I would need to run 15 gallons of pH adjusted water through the soil? I am not sure how I would do that on an indoor grow. Would it be helpful to go ahead and do that at week 8 of flower? Because my buds are not really getting as fat as some others I have seen in pictures.

 

[Emilya Green]

yes, I believe it would have been helpful especially in the final bud swell portion of the grow. When I needed to flush I physically carried all of the containers one by one into the bathtub and I did my flush there. Only the last bit needs to be pH adjusted by the way.

 

[StickyDigits]

The Trichomes are still clear, so they may have a couple more weeks till harvest so I decided to flush now and then feed for another week once they dry out in a couple of days. Here is what I did today, mid week 8 of flowering.
I flushed the plants per this protocol:
1 gal H20 with Sledge Hammer (2 tsp per gal) followed by 2 gal plain H20 followed by 1 gal H2O with Big Bloom (2 tsp per gal). All H2O pH adjusted.
I'll post my results.

 

[StickyDigits]

Now two days post flush. Fed per F.F. week 12 soil schedule plus Cal Mag. Near end of week 8 of flowering. No amber trichomes yet.

 

[StickyDigits]

Week 9 of flowering underway. Today I am seeing first amber trichomes. Will give only water from here on out.

 

[Ed Brown]

Do you think your girls needed the 5 gal bags? I did 3 gallons last grow and the plants semmed to not be restricted.

 

[StickyDigits]

Being my first grow, I don't know for sure, but 5 gallons seems pretty common.

 

[Ed Brown]

Great first grow bro! Were you training the branches to grow outwards? I just finished my first WW grow. Looking forward to seeing your harvest!

 

[StickyDigits]

I topped at about node 4 and pulled the branches to the pot perimeter with string. In flower, I defoliated, maybe too much. But we'll see what it yields.

 

[Ed Brown]

Sounds good. I'm not sure if im going to top during next grow. I think I will do a SCROG though. Do you feel like your two colas from topping were still a good size?

 

[StickyDigits]

The colas seem small compared to others I have seen in photos. So I think this first grow was me stumbling through learning how to grow while doing my natural medicine Cancer treatment full time. I was just staying about one step ahead of the plants. Next grow will hopefully have less mistakes and have bigger buds. I just received my next seeds, so it won't be long.

 

[Ed Brown]

I feel you man. I had a real hard time getting my ventilation controlled in my attic tent grow. I'm trying Gelato for my next strain.