what do YOU think the prob was?

Anyway, I've been harboring a problem. It started about 2 weeks ago.

I fed my plants, and the next day...
Browning of the leaves on one plant, not just the tips but the tips of the seraded blades on the leaves, next day.....
Very light green spots in between the veins going from main leaf vein to tips of leaf, next day....
Leaves browning and start to turn crunchy brittle and curled

Now, becauseI had just fed, I assumed nute-burn....
fast forward 1 week, one feeding since with plain water....
problem getting worse, maybe because I didn't flush?....
fast forward another week, problem still getting worse?

(hmmmm, maybe whitefly larvae. hmmmmm haven't seen any bugs at all through the whole grow)

Went to barnes&Nobles earlier tonight. Looked at a couple cannabis cultivation books. One had a description of my problem, down to the last detail. Nute burn? Whiteflies? NOOOOOOOOOOOOO
Mg deficiency, low ph. Huh, so i guess ph is important. Went to wal-mart and picked pool ph test kit (test chlorine too, oooohhhhhh).

i think it's either ph, ventilation problem (heat) or the lights might be too close.

yeah, I've thought about ventilation or heat too. But, I am using cfl's and the temp stays between 70 -85 F most of the time, and the ventilation I don't think is a prob, I gopt a pretty good exhaust fan. Anyway I tested my ph of the water today, frickin' 8.2!!!! I thought I was safe b/c it's well water from a natural spring. guess not. The ph of the soil was better, however b/c the soil changes color of water anyway, kind of hard yto tell. from now on, I will be adjusting the ph of my water. thanks for the input.