Just some blahblah for ya.
2nd pic, you see how there is a banding apearence that is almost white blotches in between the veins like steps with the center line going up the leaf blade that is still dark, losing its color from the outside going in towards the middle but veins remaining green, then leaves gets dry at the edges and crumble, I'm looking mainly at, in the 2nd pic, the left most single leaf blade of that leaf. And the problem is on the older lower leaves and would move up when/if that leaf drops continuing to affect the larger leaves only. I beleive this is Mg deficiency, I am actually certain it is, but the cause, can be a few things, as mentioned, and cure I don't beleive is just dumping some Mg on them because you've got other shit goin on.
Then in 1st pic, that is some wierd shit, it's like a micronutrient deficiency at the same time only affecting the top of the plant, immobile, sticking with the newest leaves, this all tells me you have pH issue either just out of range, or an excess of nutrients that drove the pH out of range due to high salt content(salinity) then I read you use 5.7 in coco, and if salts are too much, or fed too often, and they built in the medium, this would drive pH down even further than 5.7, which I feel is already low. Then looking at some charts of nutrients and pH, where at certain pH certain elements are locked out, and other pH values they are available, Mg gets locked out at lower pH. It's all pointing me to advise you raise your pH that you use, and check the runoff pH and EC strength coming out the bottom, to see where things stand.
Not only do I want to just give insctruction like you hand someone a book and they just follow what it says, I'm trying to explain in depth my reasoning behind my assesment so you have an understanding where I'm coming from.
sorry for so much blahblah, that's just me. Is it the weed, I don't know. Probably.