I had my first fish loss last night. I discovered an oto in the back corner lifeless. It looked healthy and happy just the day before with great coloration, so I'm really not sure what happened. The coloration and condition of the fish even looked good when I removed it from the tank. My thought is that perhaps it decided to clean the intake tube and made its way down to the bottom of the tube where it encountered the water suction and suffered some internal damage. Water parameters remained unchanged.
I'm sorry to hear that
If it's just physical damage, though, at least the others won't be affected, right?