Lost Our clown today
 

I just posted this in marine fish- We came home from work and our clown was at the bottom of the tank, gasping for air and not moving. He died within half an hour, before we could try anything.

All water parameters were stable, and the 3 other fish are doing ok (blackcap, clown, and royal gramma). I did add a couple pieces of coral 2 days ago (hammer coral, small piece SPS). I wonder if that could have contributed to it? I initially thought it was just constipation, but he was too sick too fast.

Any ideas?