Please do not continue trying to mess with the pH. Your fish will be able to adjust to pretty much any pH from 6-9. Messing with the pH and causing fluctuations is extremely stressful on the fish.
A pH of 7.6 is fine. Mine is even higher than that. Plus, the pH down stuff is not permanent. After adding it, you will notice the pH start to climb, again. This will do nothing but stress out your fish. pH changes are very, very stressful and it's best to not mess with them at all.