How long do I separate out the bully and what if theres more than one?

[Australorpismyfav]

I introduced a Isa brown to my flock after the Barnevelder finished moulting they all started laying eggs but the Isa brown started moulting and all 3 of them stopped laying eggs their is only aggression over food scraps nothing with eating from the pellet holder. and I just started feeding them black field crickets. what do I do? Does this have something to do with the crickets? Why has she stopped laying eggs like after 4 weeks after her moulting finished? Do I isolate ? The Isa brown has been alone for like 6 months all her friends died and I rescued her from my school. She prefers to do things by her self but enjoys playing with the others I'm not sure isolating ill make her less aggressive.