i have had a 55 gal. tank set up for over 2 years now..no real problems in all this time...last week i noticed my foxface wasn't eating and he had a cloudy eye..his eye was like a bluish green color..so i took a sample of water to my LFS..he said my PH was like 7.8 and my nitrates were a little high...so i added a PH buffer and changed my filter pads..i went back to LFS about 4 days later to get another test done to see if things had improved..but now my PH was like 7.6 it was at the lowest level on the test..nitrates were the same..but nitrites and ammonia were fine..so iwas told to put some crushed coral in the filter area to raise the PH..then i wated another 5 days took another sample in and the PH was back to normal and the nitrates were fine but now my ammonia was .25 and my nitrites were .25 ..my fish were dropping like flies..lost the foxface ,bi-color blenny, royal dottyback, and a damsel..i notices some of the other fish not doing well and some look like ick ans some look like they had a fungus..so i moved the rest of them into a hos. tank to medicate with copper meds...my question is what happen to my tank..i have always kept up my tank maint, and water changes..i have never had this prob. before..never put meds. in this tank ..just food..