Discus are a schoaling fish, they really like to be in groups, but when i say group i dont meant 2 or 3.
If you have 3, 2 will usually pick on 1 and you'll lose that one. Same with 2, one will always pick on the other and hence youll lose the other.
Amazingly discus are quite agressive fish, especially between themselves. I would keep a group of around 5 for agression spread which you will experience especially during feeding time.
A group of 5 should be housed in a 55gal tank minimum, 2x filters and plenty of heat but thats par for the course with discus. I think the general rule of thumb for discus is 1 fish for 10gal.