Leaves rolled down

Hi,
This is an unknown strain. It's under 600w HPS, grow room temps 25-30oC
I treat these two plants exactly the same as my other two (white widow) which are happy. The leaves have been like this for a good few weeks. I've tried more nutes, and less nutes. I've watered them loads, and i've let them run very dry. Still no change.

Any ideas?

thanks

Over fertilization will make your leaves curl down, these may comeout of it, but the leaves that are curled may die. Plant could die also depending upon the extent of burn

looks overwatered too

Thanks,
Definitely not overwatered. I've run it pretty dry a couple of times, to the point that the leaves are all drooping badly. Once watered, they stop drooping, but the roll still remains. I'll try not fertilizing for a couple of weeks and see what happens. The plants are generally quite ok, and are still producing good bud.

Could be a bit high humidity. Are you getting high temps with high humidity too?

low humidity and high temps. I did have a lot of issues with temperatures getting far too high. I've sorted it out now, and rarely do the temps exceed 31oC, humidity is pretty low, about 30-40%

its probably just still a bit warm then really. 30c is what? about 90f? Close to 20% over ideal temps. It will affect the growth. Perhaps run a home made co2 adder? That could be productive