Cause of death?

[JoeBoxer]

In my experience, panda corys aren't the most hardy. I wouldn't be surprised if he caught some weird bug and his immune system couldn't handle it. That or he was sick in some way and it just took his life.
The fish I originally mentioned were sick. I just never got a real diagnosis on what killed them.

Okay good to know. All three never really looked right from the beginning. Pretty sluggish.

I would say the shark did it. Red tails can be highly aggressive to tankmates.

That was my first thought but I've been sitting and watching them a lot and never any signs of aggression at all.