Edges Turning Brown Help

I will try and give everything relevant that I can. Here goes.

I brought in 12 clones one week ago. They were all rooted in small cubes with at least 3 to 6 roots poking out. The color on all was good. They are BB WR and Kush. They are all in bubble buckets with drip system and are under a single 1000 watt MH. The temp right by the top of the plants never goes over 76 degrees and is very steady. The light is cooled and I can put my hand on the glass and it is not hot. The light is about 24" away from the plants.

I am feeding with Botanicare Grow mixed at the rate for seedlings and cuttings and I am also adding cal mag and superthrive to the mix. The Grow alone adds about 400 ppm with the cal mag and superthrive it bumps it up to 650. The water is RO water and keeping a constant PH has been a problem I set it to 5.8 and the next day it has gone up to 7.0 or even higher and I repeat the process.

The plants have not done much other than get slightly yellower everyday and now the edges of the leaves are turning brown and are curling up slightly. The Kush is not turning brown on the edges but it is getting lighter in color and not growing.

you answered it with the ph swings, cant be going that far out. the ph will rise till its where it realy is,. can take some time. or the rez isnt big enough for the plant count and when they feed its effecting the ph in the rez. usualy is cause people dont use big enough rez for counts. i leave my food mix an hour till its set to the right ph then use it. and temps play a factor on the ph as well. and try it at 5.5
the brown curling leaves in veg is most likely phios deff.

you may need to adjust the ph a few times a day till its stable...and all the time if the rez is to small