Don't mean to hijack your thread, but I am having a similar low pH problem in my QT tank (currently occupied by a small blue tang & a cleaner wrasse).
I tested the water this am: pH 7.8, Ammonia .50, Nitrites 1.0, and Nitrates 40. I have mixed & aerated SW ready to go and I plan to do a partial water change & clean detrius off the tank bottom in a little bit. I'm using a HOB Whisper power filter. Should I try to raise the pH with a buffer or will it go up by itself when the Amm/ites/ates drop back down? Can I use API pH Up (their website says it is for freshwater)? (BTW, the pH was at 8.2 before I put the fish in the QT last weekend).