Clown not looking too good

[pa1ntbru5h]

Hi everyone,

 

I recently brought 2 clowns home from my LFS. They looked great the day I bought them and were doing great for the past 3 days. They seemed to have paired because they would stick together when swimming around. No sign of aggression toward one another. Then I wake up to one of them dead on the sandbed! The second clown has this white stuff on his top rear fin that looks like it could be rotting.. He's swimming around, but definitely not as active as he was before.

Any help would be appreciated.

 

Water Parameters:
pH 8.2

salinity: 1.024

ammonia: 0 before clown died.. was ~0.25 when i woke up because of dead clown im guessing (water change already done)

nitrites: 0

nitrates: 0

alkalinity: 8.7 dKH