Nut burn?

Well, it was really popular among certain groups, not to be named, to suntan their taints in the last few years. I'd expect that accounts for some number of nut burns in recent years, lol. organic is irrelevant. If it's been given too much, it's going to have a toxicity. I think you have something locking out K, but could be wrong. that substrate is just freely lying on the floor? Looks like it has shifted and cracked etc, which would likely cause root damage. Looks pretty dry too, but that might just be timing of a photograph. As long as you water when top layer starts to get dry and water entier thing without dry pockets, all is well. If soil or spagnum peat moss based substrate, wait fro dryness to be close to 1" deep and coco-based substrate i'd re-irrigate the moment it starts to turn color on top. It's a little hard to do that when you have no drainage and the soil is just sitting on the floor. If you weren't fully getting the substrate saturated each irrigation cycle, you get dry-pockets with an ebb and flow of moisture which deposit nutes, organic or not, that will then go back into solution and potentially causing an elevated EC in that pocket of substrate, because it's adding to whatever fertilizer you've used - each time that ebb and flow of moisture occured since the beginning. No fertilzier for 10 days might not be enough to correct an issue like that if it was occuring the entire grow beforehand. you've made things more difficult by your methods, and also tougher to diagnose due to elevated risks of buildup in substrate. the leaves with bends are likely due to some fluctuation in pH - faster and slower growth rates over time cause the crooked/bending in leaves. The tacoing type of contortion is likely environmental. Usually symptoms that involve the serated tips around edges of the leaves is related to K. pH-related causes would likely lockout other things first, so we can eliminate that for the most part. Could be lockout from another nutrient's high concentration or a little underfeeding of K. The leaves are quite lush (dark) so both are possible.