at the start of the week i noticed a few white spots on my cardinals fins and tails, which at that point looked like white spot. so after a good clean of the gravel, rocks and all decor and a 50% water change. i treated for whitespot, my treatment was also effective on velvet. but now they have more spots all over the bodies and are missing parts/or whole fins and tails, and in the last 24hrs 3 have died. i have watched the tank a lot and never seen any nipping or chasing. its a community tank and nothing else has any symptoms at all. Whats wrong with my cardinals?