Please need help for a beginner. Two of my fish died this morning within 30min from eah other. A Cochus Blue Tetra and a red platy. Both had symptoms of possible velvet disease, white spots that started on the fins and tail. They suddenly started floating upside down with out any control. What could possibly be the cause?? I have removed them from the main tank and placed them in seperate tank. Sera Oodinopur was added to the water in the separate tank but they still died. How will this affect my other fish?? The water condition are all normal within the parameters. Please help.