Leaves changing colour, is this bad?

[johnrinson]

I have four plants, about 2-months in to their grow. They've recently started changing from a healthy dark green to light, lime green leaves.

Until recently I'd been using a 600w LED light - and I recently added a second, identical 600w LED light. I did this because my last grow of four plants had a bit of a disappointing yield so I thought doubling the light might help boost it this time round.

Within a few days this changing colour happened, so this, I'm assuming must be the cause. I immediately raised the lights higher - a good 24-inches above the canopy - but the lime green leaves are still appearing in more places.

- Are these colour changes a problem? Am I killing the plants / harming the yield more than helping?
- Should I revert back to one light?
- Should I keep two lights but do something different to help resolve the problem?

Here's a photo showing a bit of what I'm talking about.
Thanks!

 

[Joshualuck]

She looks beautiful man shes looks to be growing lovely. Just make sure your nitrogen levels are cool. The dark green is a sign of nitrogen deficiency of having to much. You want her to be a in between dark and light. Looks like your girls are starting to go through her nitrogen in her soil. I had over dosed my girl in nitrogen and her leaves were dark waxy looking. when I flushed her, her leaves went 3 shades lighter but still was growing like a weed so that's all I did. It looks to me that your nitrogen was a little higher and adding that extra light made them use more nutes and grew more in the process. I wouldn't do any thing just yet but watch for a while longer. But if shes still growing I'd say your nitrogen was a little high. Here are a couple of pics of mine before and after.

BEFORE FLUSH:

AFTER FLUSH:

You can see the difference in her leaves. Nitrogen was my issue and it wasn't that bad. Easy fix looks like your girl is fixing her self.

 

[bobrown14]

@Joshualuck you're running in hydro - the OP is in soil.

Flushing soil is not the same as flushing hydro.

Actually its 180 degrees opposite.

@johnrinson your plants will be fine. Next run dont change things mid stream just do what you do all the way thru. Changing things like lighting specially X2 amount can be a problem. Best to gradually change IF you want to change.

For yields - its mostly gonna be genetics.

If you want bigger yields you need bigger roots. The old saying bigger roots bigger shoots is true. Dont top your plants that will reduce yields.

Usually yellowing or lighter colors indicates that the plant is lacking something likely something in the soil. Or it could be new growth and everything is good.

Whats your soil mix and are you using fertilizers??

I suggest moving your lighting closer a few inches every day. Are you in flower 12/12 lighting yet?? How long ago did you change your lighting schedule??

 

[johnrinson]

@bobrown14 thanks very much - I did think perhaps if I hadn't changed part way through it would've been better. I've got bigger pots this time, hoping for more root space.
The yellowing isn't new growth, it's existing leaves that were a deep green suddenly turning yellow. I've been feeding them plenty of organic nutrients. I'm using Biobizz All Mix soil and nutrients. Still in veg at the moment. I added the additional light just over two weeks ago and the yellowing began almost immediately, literally within a day or so and has gradually spread since then. I had the lights low down though, and have since raised them up as high as possible but as yet no improvement in the yellow color

 

[bobrown14]

Try some kelp and ewc tea.

Looks to me like new growth is yellowing which points to a micro-nutrient deficit and/or Calcium deficit.

Kelp meal will have all the micro nutrients the plants need to grow, the EWC will help with the same plus beneficial microbes.

Still in VEG its probably not an issue with lighting.

 

[johnrinson]

Thanks for all your advice. I've just checked on the plants again and the one suffering the worst has got even worse. It's now got some signs of leaves dying and is yellow all over. I'm really worried it, or all of them, are dying. This is only my 2nd grow - I'm using exactly the same nutrient schedule as with my first and didn't have anything like this. Does this look like a terminal problem? Or recoverable? Thanks again!

 

[johnrinson]

Just for info for anyone else experiencing a similar problem, I believe I've discovered the cause of the problem - which is related to lighting. As mentioned in my OP, this leaf yellowing started when I added a 2nd light to the tent - but I've just discovered that when I added that light, I hadn't correctly set the timer, so the 2nd light was staying on 24-hours a day (the first light going on and off on the 16/8 light schedule). I feel like this surely must be my problem. I've corrected it now and really hoping the plants recover in time for flipping to flowering mode. Below is a picture of my worst affected plant, which now looks awful. Really hope it recovers!

 

[Emilya Green]

It is my belief that your additional lighting has simply increased the nutritional needs of your plants. I see an iron deficiency here. Usually this is pH related. Please tell me what you are doing to manage pH of your incoming fluids.

 

[johnrinson]

Hey @Emilya thanks for the advice. I'm not doing anything to manage the pH at all (I'm not sure what I should actually be doing) so you could definitely be right. I'm just using organic nutrients - Biobizz Grow, Biobizz Fish Mix and I've just started adding CalMag after a suggestion above. What would you recommend I do to increase the iron levels?

 

[Emilya Green]

What would you recommend I do to increase the iron levels?

The iron is probably there in your nutrients, but is unavailable to the plants because of your pH. From the biobizz website, FAQ:

Is it necessary to regulate the pH when using the Biobizz products?
In general, when using organic nutrients, pH adjusting is not necessary. This is because the Biobizz products tend to lower the pH naturally until it comes to the optimal range of 6.2-6.3.

However, in some cases the base pH of the tap water can be too high or the grower chooses to use RO water with a very low pH. In those cases, you can use Bio·pH+ and Bio·pH- to regulate the pH of the mix before watering your plants.

 

[johnrinson]

Just for anyone following this or experiencing a similar problem in future - I bought a digital PH meter and have measured the PH of my soil and also of the water (including nutrients) that I'm watering the plants with, as suggested by @Emilya above. Both showed as PH 5.9, which I'm guessing is a little low, so will purchase some PH+ to raise it.

 

[Emilya Green]

Just for anyone following this or experiencing a similar problem in future - I bought a digital PH meter and have measured the PH of my soil and also of the water (including nutrients) that I'm watering the plants with, as suggested by @Emilya above. Both showed as PH 5.9, which I'm guessing is a little low, so will purchase some PH+ to raise it.

Hi @johnrinson and welcome to the forum!

Sorry to be the one to have to tell you this, but unless you are measuring your soil pH in a vacuum and by using a slurry test done with exactly equal amounts of distilled water and a representative sample of your soil, you didn't do a proper soil pH test. Soil pH is also confusing in that there is a base pH, and the pH that the soil assumes when you water with a fluid set to a definite pH. Did you realize that the soil's pH actually changes and is different in different parts of your container, depending on how wet the soil is in that region?

I seriously doubt your soil is set to that low of a base pH... that would be for orchids and other acidic loving plants and that acidic soil would be killing everything else. Most potting soils are set with a base pH near 6.8, or to the high end of the 6.2-6.8 pH range, so that the soil can help provide an upward drift to the pH of the container after you water with fluids set at the low end of this range. Please don't try to adjust your soil... it is most likely just exactly where it needs to be. Base pH, water retention rate, and water flow through rates are just some of the things that go into the production of a soil, and the scientists that do this for you really do know what they are doing.

In a soil grow, using synthetic nutes designed to be mobile in the 6.2-6.8 pH range, simply adjust all of your fluids to the low end of the scale, typically 6.3 pH, and then the soil will do what it does to make sure that your nutrients are able to swing through that entire range, picking up each nutrient as it becomes most mobile.

 

[johnrinson]

Thank you @Emilya that's amazing detail and helpful, thanks very much. So my fluids (water with organic Biobizz nutrients 'Grow' and 'Fish Mix', plus some Calmag - the PH of that mixture (according to my digital PH meter) is 5.9. Would you pH+ that up to 6.5 ? Thanks again.