big brown spot and tips burnt??

[slickdawg]

what could this be? ive used vary lil nutrients! and it’s only a a couple leafs some new some old! would me playing with the Ph cause this?


indoor grow box (soil
40”h 28”w 28”d is my box
have a led grow panel 13" with full spectrum and 225 LEDS got 1 plant she’s in week 7 in vegetation “Krippler”
im doing LST training on my plant
i have a passive exhaust system with a fan for air flow