nitrate 0-20, nitrite 0, hardness soft, ammonia 0-.25, ph is somewhere between 7.6-7.8. Those are the parameters for my tank. I have lost 3 fish in the past two days. What seems to happen is that they start to breathe heavy and become less active. Is weird because them seem to swim fine for awhile then just drop to the bottom. There are no visible spots or anything. Its seems to only be affecting a few at a time. I just hope I don't lose all of my fish. Any ideas?