Hello, welcome to Backyard chickens. Are hens pecking on each other, or is is mainly roosters ganging up on hens? I know in my flock, a rooster will get a hen and start mating with her, then the commotion attracts the other roosters and they literally take turns mating with the hen. The hens have gotten smart, and run away as quickly as possible now. I suggest rehoming the two roosters, whichever ones they may be, to a new flock, you may just have too many roosters and they are creating too much tension with in the flock. Also, what living environment are they in? Do they free range, or are they in a run? If they are in a run, what are the dimensions of the run? Often, when chickens are too crowded, that will lead to cannibalism and feather picking. Hope this helps, and have fun on Backyard chickens!