I know of very few (read: none) folks who used ph decreasers and kept their fish healthy. A ph of 7.6-7.8 is fine, and it's what your fish are likely used to in the store. I would stop messing with ph immediately.
drgold, thanks for the advice with the ph. I think I'll try that and see if I have better luck. I would think that one less chemical in the water would be a good thing for the fish.
Regards,
Joe