I'm having the same issues.Growing out a group of 10 sevs from 2-4", and they are really hard on each other, even in a 4 foot tank. You can see the territorial nips and constant lip locking.
I guess the exception proves the rule.
I’ve kept a group of adults in a 75 for several years without issue.
I have an orange shoulder that established itself quickly as the boss, but I think they were all males.