He beat me to it, but yes exactly what Marine Edge said.
Whenever you buy new fish they should be monitored in a quarantine tank.
At the very least keep them there for a week, and treat for internal parasites.
That way your show tank, or display tank doesn't die from a single new purchase like an exploding discus.
P.S. sorry for your loss and I know it sucks to lose pets and the money spent for them, but just say Exploding Discus out loud, it's funny.