I have a 10 gallon quarantine tank with a heater, seeded sponge filter, and some silk plants. I just got a school of cardinal tetras and I put them in the tank. They all looked healthy at the store and no signs of disease. I dosed the med trio for preventive measures like Cory says. I have also tried dosing salt with no luck. They all die off one by one per day. Water is fine with 0 ammonia and nitrite and 10ppm nitrate 78 degrees. Why do my fish not make it past quarantine?