If it was heat a typical leaf with heat stress that bad will show the leaf edges cupping up.
If it was fert burn typically the tip is going to show more damage than the edges of the blade.
stinkyattic Reviewed by stinkyattic on . Will heat cause brown edges? I am in the second week of vegging one plant. Everything was beautiful last night, but when I woke up this morning the edges of a few fan leaves were brown. It was actually pretty hot in there, so I think my lamps were a little too close. I raised them, hopefully this helps. Just wanted somebody to confirm that heat is the problem and that it's not a problem with soil, etc... Rating: 5