I really think you need to find a way to age your water before water changes. I think that playing with the PH like you are trying to do is just asking for a lot of trouble. PH is a funny thing in how it works and can be affected by so many different things. Unless you are experienced in how to properly work with the PH then I think you're better off leaving it alone.
Do you have a water softener? If so, is there a way to get water from a faucet that is pre-water softener?
Do you have a water softener? If so, is there a way to get water from a faucet that is pre-water softener?