singed white hairs

I have noticed on one of my plants it has slightly singed hairs even though it is furthest one away from my lights 1x600 and 1 x400 hps my other plants are ok i was wondering could it be nut burn someone please help

pics would help but info will also, are the hairs turning red? what light schedule? how long or how old is the plant ??? info,info

were these eary pre-flower's? how long did you vege after they showed their sex? are you still 18/6? How long 12/12? Let us know! jack