If I wanted a pair of JDs, I would have only one male, and get 3 females. the male and one of the females will pair up, then get rid of the other females. if you don't want a pair (they're gonna mate), I'd get rid of the submissive male and get fish of a different species. those two JDs are going to continue to fight.
A green terror or a blue acara would go good with a JD in a 55.