nute burn or deficiency?

Im growing in coco and compost mix 50/50, Im using the same mix from my last crop, which thrived. Now these ones look fucked.. I've been growing for years and never had dramas like this..I've flushed them, did nothing, I've added Epsom salt, then they looked even worse, flushed again a few days ago then added some lime cos now I'm guessing the ph has dropped and causing nute lockout.. what do yas reckon? If it is nute lockout, how long will it take for them to recover after adding lime?

Have you changed your lighting? What are your temps?

I've got it under a 150 MH.Dunno what the temp is but I know it was a bit too hot cos I could tell there was heat stress on the leaves so I raised the light up yesterday.. do u reckon just the heat would cause them to look so unhealty tho? There is also a fungus gnat problem which I'm working on.. the fuckers are soo hard to get rid of..