what is wrong with my plant in the corner??

is this nute burn? seems like one of the fan leaves is turning alittle yellowish and then today the edge kinda burnt. on the smaller lower leaves, they have yellow outlines on the edges, as you can see... its directly under the hps, but it passed the hand test (to see if it's too hot.)... not sure what the problem is. any advice?

week 1 and a half from clones...


earlier...



thanks. also.. is it time to enter flowering?