AuldKeltanswered grow question 4 years ago Sox,
To accurately determine the problem would require too many exchanges back and forth, and you don't have time for that. I'd suggest you immediately go to growweedeasy.com. In their top banner they have a "Problems & Symtoms" link. Since you know everything you've been doing, using their information you can most likely find your particular problem.
I will say though that the burnt and curled tips point towards an excess of nutrients, not a shortfall.
Good Luck!