yellow on a leaf what would be the cause?
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Need more info
Can be a PH issue
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coco ph 6.5-6.6 3 gallon grow bags 600 watt mh and 1200 wt led in middle
new ph pen coming today nutes gia green 50/50 4-4-4/2-8-4 top dressing and worm crap watering with filtered tap water folier spray once a week with light cal/mag soiless straight up coco-perlite 70/30
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Not a coco user
I had a similar issue my old pen was way off when I used new one wow it was way off
I use pro mix and I keep my ph between 6.0 and 6.2
Is this on lower leaves or on top
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lower leaves
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Maybe not relevant to your issue but I like the pH drops as a backup. They may not be super accurate but they’re never wrong. Also a good way to see if your meter is on point.
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Also maybe be root issue
If plant , coco is too wet
Of heat related
My $ on PH
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That may be a bit close to the plant on the far right. Judging by the fan leaf size posted, the plant in question is the far right one.
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Was thinking the same thing
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nope one of the ones in the middle under led
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Ok, i would still probably raise the lights a bit until the issue is solved, just in case. They look fairly healthy… Sorry.
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Ok I see you spray with calmag
Add a bit of Epson salts to your feed regiment
Plants under led needs calmag and or Epson salts more then others
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Hay olschool 
I grow in coco and try to keep the pH right on 5.8. Seems like the sweet spot for best Ca and Mg absorbsion, and everything else too.
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I knew there was a big difference in ph but was not sure of the numbers
Thanks
Paps
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Is that the extent of the yellowing?
Judging from the rest of the leaf it looks healthy to me, if it’s isolated to that i would ignore it and not worry about it, overall it looks healthy imo.
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Coco looks like dirt, but it isn’t! Took me a while for that to sink in!
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I agree, looks like Ca/Mg related issues which are common in coco. First off, pH should be between 5,5-6,2. Secondly, due to the cation exchange capacity of coco, there’s a general need for higher levels of Ca/Mg in the substrate compared to soil as some of it is directly absorbed and stored by the fibres, making it unavailable to the plants.
Before deciding on a course of action you should find out the Ca and Mg levels of the water you are working with. Depending on what they are, you: either need supplement one of the two elements to bring them into a balanced ratio (Ca:Mg 3:1), supplement both elements to generally increase the cal/mg content of the solution or supplement one element to bring it to a balanced ratio before adding further cal/mag to increase the overall concentration.
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I would.drop your ph to between 5.8 and 6.2. You are running PH to high bud.
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thanks waiting on a new ph meter today thought that was what it was just wanted to get a consensus
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appreciate all thde input thanks
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