Guerilla grow leaf problem

Looks like a mag deficiency from here.

I can throw in a tip for guerrilla grows : save your banana skins, dry and powder them, then just sprinkle generously on ground each chance given ;-) .

Your right there on it not being magnesium. My bad.

This is a potassium deficiency

To me it looks more like a potassium deficiency. A magnesium deficiency would affect the whole leaf, not just the edges.

Looks like a magnesium deficiency. Have you been using a cal mag supplement. If not it may be wise to. Also it could be a incorrect ph stopping your plant absorbing magnesium.