Could be leaf burn from foliar spray, mold, fungus... hard to tell from the pics.

Isn't a PH of 5.7 a little low? Tap water? Might consider leaving it out uncovered for a day or two before using it.

Maybe time to stop feeding for a few and flush. Low PH might be causing nute lockup.
greenbastard Reviewed by greenbastard on . brown spots?!?!?! need help asap not too sure whats going on with my plant... shes a month old, started from seed, growin in a bubbler system, ph 5.7, temp 82, under 5-26watt cfl's 6500k..... ok soo shes haveing some problems... a few leaves are twistin, some have brown spots, some at the edges and others all over the leave.... so in tryin to fix this problom, ive made sure to keep a constant ph @ 5.7(something that used to vary from 5.5-6.5) and more brown spots appear... changed the water, mixed in nutrients (ecogrow Rating: 5