I have a Procyon and a lightblaze 400 and if I get my PPM above 500 I start to get N spots on the ends of my fan leaves and that's on 4 1/2 week old veg plants in a drip hydro set up. At week 5 I flower 16" to 18" plants from clones. If I keep the PPM at around 400 to 450 the plants love it and that's also keeping the LED's 20" away. I have been doing the same strain for about 4 years now and veging under HID 15" to 18" away I can slam the PPM up to 1,100 by 4 1/2 weeks with out one spot on them. So my experience so far is plants under high powered LED's do not like a lot of food. Don't get me wrong it's a good thing but it's something to keep in mind. To make a long story short I use half the strength of nutrient and it works awesome. LOL