Nutrient deficiency?

You need to flag the dead off right away and given them a very low mostly water solution with vitamin b , calcium and magnesium stat bro

Hi I think you previously had nutrient burn. That is why the tips are brown and wilted. These leaves, however, are higher up and look like calcium / magnesium deficiency. But this could very well be caused by either: PH too high or low, overwatering, end of flowering. So stop adding anything containing nitrogen. CalMag also contains nitrogen so carefull. If you are able to obtain some Dolomite (garden centers) or some lime, also to aid in the PH if too acidic. While you are at it, add some epsom salt, you seem low on sulphur too... Some strains use up a lot more calcium and magnesium when under LED. Also when feeding too much nitrogen it can block out other nutes. Good luck!!!