Yes, cichlids defend their young violently and hence why I was saying that the 55G was too small for them. I would take the fm's to the lfs to be traded in or if another 55G can be purchsed just for them, that would be best... not just because of pestering the couple, but because they can be seriously hurt from the jd's with their strong parental instincts.
Also, both male and female JD's will have the characteristic purple/teal/green speckling all over the body. Males are typically larger, but more telling characteristics are the fins (males have much longer and pointier tips of both the dorsal and anal fins) and the speckling at the jawline/gill plate. Females speckling continues onto the jaw and gill plate while males will have very few spots, if any at all. If the female (the smaller of the two) is just a dark black with very little color, then it seems to be overly stressed (cichlids show emotion through their skin coloration like humans have facial expressions).... pictures would be good.... im assuming the smaller is the female right now, but if it is a juvenile male that is not yet mature enough to fertilize eggs, then the female could be stressing it in trying to fertilize the eggs and hence why the smaller of the two is darker, and more stressed.
About how big is the larger of the two?