AGGRESSION HELP

Hey team , so I got 4 Red head Tapajós aka Geophagus pyrocephalus, I got one first for about a month than I added 3 more last week cause I read they prefer to be in groups , however the original chases and tries to nip the other 3 and does not let them get close to it, while the other 3 get along just fine

Is this a form of them establishing hierarchy, should I wait longer ? Or remove the aggressor ?