benggai cardinal

My benggai are probably both males and fighting each other (fluval 13.5). I moved one into a quarantine 5 gal (not ideal) and need advice. Do I add a female, then reintroduce the third? Or add a female to each tank? Thanks coral friends!

Hey coral friends! BACKGROUND: I got both fish as juveniles, are now a few months old. In a perfect world, one would have been female, but perfection will not come. Separated from each other for a week, and tried to reintroduce the victim fish, and the bullying continued. At this point, I...