Dead clownfish

[Perthegallon]

Hello guys so my friend I help set up a tank about a year ago has 2 clown fish a starfish and a few snails. Well anyways he does a water change 50% two days ago and he got home last night and one was dead so he did another 50% water change and checked salinity and checked others nothing looked out of the normal his starfish and other snails are doing fine but the second clownfish just died today.
so I was wondering if anyone has any ideas of what this could be as I don’t think it’s a pest since nothing new has been added to the tank in months.

 

[Poof No Eyebrows]

I guess first question would be why a 50% water change to begin with. Second would be why do another one right after (which could have contributed to the death). Kinda hard to diagnose without knowing any details. Was the tank having any issues prior to the large water change?