Yes I use RO water, some calmag as recommended (a little less than 5ml/gal actually), and weak gh 3 part nutrients. 5ml each per gallon currently.

I recently added a 400wMH and my water temp has gone up too high, does that create a PH issue?

My plan already for today is to drain the system, relocate my res to a new location which I've tested as several degrees cooler. But I dont know if thats related to ph. I also planned to go to latewoods feeding schedule which will be somewhat stronger nutrients.