I have 4 discus in a 120 and I know they have a pecking order but lately it seems like they are pecking a little too much. They are all about 5 to 6 inches. They have been doing things like getting in each others faces and flaring their gills and pecking each others mouths or getting butt to butt and moving their back fins quickly. My main problem is that they have seemed to have really ganged up on one discus. They all pick on each other but they all pick on one certain discus. Which is weird b/c it is the biggest one. But it actually has bite marks on both of it's sides that I just now noticed. Is this a breeding thing? Are they even big enough to breed? All help is welcome. Thanks ahead of time!