I'm growing under one of the LED's, Advanced Platinum Series P300 300w, and a Emily's Garden with a 4 gal reservoir. The light is set at 18" above the seedlings. I have the pH Test Kit (I know, I know - but I can't afford anything else right now). I fill it with distilled water and add the recommended measure of FloraNova grow to it. Every day I test the pH, and every day it is extremely low, -4.0 and down. I put a couple of CC's of General Hydroponics pH up in the reservoir and the pH goes back to normal, but the next morning, the pH is down again. It seems to be down the same amount every time, by my imprecise measurements. The growth is stunted and slow. The bottom leaves are yellow. This is the first time I'm growing under the LED's. I've grown under the MH lights before and it was fine. I washed out the reservoir, again, with distilled water - no result. I changed my brand of distilled water - no result. I've changed the reservoir three times - no result. What could be happening to the pH every night? Or is it just a symptom, something else is going on?