Hello to my favorite forum!
I am struggling to address this issue. I thought it was a calc/mg issue but now I am thinking maybe lockout or something? I am so confused as to what it could be.
Coco coir indoor grow. 4-4-4 and 2-8-4 Gaia green organic, 750-900ppfd, ph 6.15-6.8, fish shit every other feeding and recharge tea 1xweek.
My first thoughts, looking at the last picture, dark green leafs .I’m thinking a little heavy on nitrogen. See what other members think. good luck moving forward.
Hi I agree it’s dark green a N problem partly well I think more than that too not liking the chlorosis and shape of new growth, suggests lockout or pH, coco uses pH5.8 to 6.0, keep your ppm numbers in a good range whatever that is and in coco fertigate til good runoff every time
All of the above with a calcium def.
Yellow between the veins is classic magnesium deficiency but could be locked out due to high nitrogen causing the dark green leaves. Hard to pin down without more info and runoff numbers. Also, your ph is high enough in coco to lock out nutes. Coco needs frequent feeds with plenty ( 25 percent or more) runoff and should be at 5.8-6.2 with lower in veg and high end during flower.
I should clarify. I used coco loco which is close but not straight coco
Runoff is 6.15 as of yesterday
Coco Loco needs a PH of 6.2-6.8 so your a bit low for it.
Ok I am at 6.35 watering today I’ll raise it slightly.
Went ahead and raised it to 6.6 and will check runoff. Thanks for the suggestion.
I’ve run all my soil grows at ph 6.5 and it seems to keep my ladies happy. I’m thinking your Ph is a bit on the low side. And yep treat coco loco as soil for the specs. 
