300 PPM? guy. my water comes outta the tap at 300PPM, your STARVING THOSE BITCHES!
what feeding method are you using (slap yourself if its not Lucas)
first off, that looks like the clearest caste of mag def i've ever seen, so, epsom salt FTW, 2nd, 300 PPM??? ZOMG! third.. 300 PPM, seriously?
http://www.drugs-forum.com/growfaq/1654.htm
edit: also, what PH is the water? and what are "high temps"