We have a 25 gallon tank with four goldfish in it (yes, we know that's too many). It's cycled and after testing the water, the only thing that seems problematic is the pH (nitrites and ammonia are zero, nitrates were normal), I believe it was 7.6. One of our fish is sitting on the bottom of the tank with her fins clamped. She's been doing this off and on for about two weeks, but she seems worse the past four or five days. She is still eating and swims around a little bit after eating, but spends most of the time sitting on the bottom. Her cheeks are now looking raw too. My husband did a 20% water change, waited three days, did a 40% and waited about a week, and then did another 40% two days ago. Any advice? What could be wrong?