hey bud! ... that's nute' burn starting,... light roasting wouldn't affect just the tips, and the damage is very different looking, and would be covering a wider area of the leaves (where max exposure is, just like on us!)... bleaching would follow the same pattern, just without the dead/dying tissue.... you're right though, too close on LEDs can light fry just like any other source.... ease back on the nutes, and keep watch on further advancing,... if it does, go to LHT for faster help!