I still have no idea what caused the deaths. The water was crystal clear yesterday, and the filter is still running like a champ. Nobody, but me, goes into the room where this tank is kept, and there were no chemicals that would affect these guys, but not the other inhabitants. I'm at a complete loss. I don't know whether the fish caused the cloudiness, or the other way around. However, this does mean I get some new monsters, hopefully a black aro is in the future.