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.
Each generation imagines itself to be more intelligent than the one that went before it, and wiser than the one that comes after it.
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.