Hello there

I am pretty worried about my hot peppers. The leafs curl up at the end of their light period, at the beginning of it (so pepper�s morning) they look much better and healthier but at the end they look just like that.
I have them under 2 MH lamps of 600 watts which are 60 cm away. The ph is 6.5 and the ppm is 925.

Do you guys have an idea why that maybe? Or also, why do they look better at "sunrise" than at dusk?

Thanks very much for your help.