I recently did a 50% water change to my 55, 45, and 20 gallon tanks. They both have filter and are heated. My Black Ghost in my 45 gallon was showing signs of distress (white streaks) and so I did another 20% water change with salt and dechlorinator. It seemed to be doing fine in the morning after and the water was clear. The morning after that, my black ghost and red-tailed shark was dead and my angel fish has a clear-ish bubble on his one eye. His fins are also a little tattered. There is one more fish I'm not sure of the breed, and he seems to be doing just fine. The tank water is cloudy. I checked the pH and ammonia levels with a couple test kits that I have. The pH is 6.0 and the ammonia is 1.0. The water in my 20 gallon and 55 gallon are clear, but there are a couple fashion my 55 that have Died. I have raise the temperature and have been treating the tank for a couple days now. I've had two Cory catfish that have died so far.