GB,
If you are trying to have balance in your RO water, just make your own remineralizing mix, or just buy RO Right.
http://forum.simplydiscus.com/showth...ter&highlight=
What exactly are you try to get from your water? You should be storing your water in a holding barrel. Then get your desired TDS (PH won't matter since your RO water PH is usually stable at 6.6 (+ or -). Once you add the mix I am suggesting, your RO PH should not change and now you will have stability.
Let me know if you have any other concerns.