Topping off question (using RO)

I would like to know, if there are any RO water users out there that could help me out on how to properly refill my 5gal DWC buckets.

My main question is: Do I use pure water, or do I add cal-mag to the water that I add?

Usually if my PH has dropped any, I use just plain old RO, and if it has risen (more often the case) I add cal-mag+ to it, making the water around 150ppm. I have not seen a need to use any nutrients on the top offs yet, and I do not believe I am ready to make that step up yet.

So how do you RO users do your daily top off's?

DWC has proven to be a pretty big learning curve, but I found that when I top off with pure RO water, my PH stays pretty darn close to the 5.8 I set it at! Just figured I would throw that oout there, since someone might be able to use the information in this thread.