I recently had a fish die and I did remove her asap from the tank however I am unsure of what it was that killed her and am worried for my tank. The deceased fish was stuck to the filter when I found her, while she was still alive, and she looked skinny. I haven't noticed her getting so skinny till it was a bit too late. When I had her in a floating hospital tank, she wouldn't partake of any food and I noticed she was a bit bloated yet still so skinny. The next morning I found her freshly deceased and curved inwards towards herself. Should I be worried of it spreading? What killed her?