MrStinkyanswered grow question 3 years ago It could be a few things:
Clawed new growth could be EC, pH or toxicity related.
The yellowing leaves suggestive of calcium issues, either too much or too little. This can be a result of pH being out of line, too much calmag in your feeds (are you using tap water or RO water? Don't forget tap already has calmag and RO has nothing in it at all). If calcium is in too high levels it can block other nutrients so can cause a series of issues quite quickly.
Might be worth a flush - as you are in coco you can flush and try to restore your medium in just 2 or maybe 3 waterings so youbshould be able to pull it back to a baseline quickly and start it up again.
Suggestions -