Does your farm store sell a chick grower or an all-flock? If you can switch to that, and offer oyster shell for calcium on the side that would give them more protein, usually around 20%.
I put cinder block steps in my run, mini perches along the fence under my raised coop, and a raised pallet to climb on & run under.
Although many people frown upon treats, I pick a clump of clover or dandelion every morning for the girls to scratch through/pick at. I don’t consider that a “treat” as if they were free ranging all day they would get a lot more grass than that. My girls also get to go outside in the gsrden for a few hours every afternoon if I am home. Dried fallen leaves are wonderful and they love to scratch in them (last year I saved 8 garbage bags full, and would replace every so often.) It would keep them busy for days.
Good luck with your girls. If you have time, once you let the “bully” back in, if you see her start pecking someone else, just give her a swift poke. Might have to do that a few times but it should deter her.