This may have become a habit, even if you resolved an original issue like protein. I suspect that picking on each other must be the chicken version of smoking to pass the time. Maybe they just need more to do? Mine seem to be amazingly active animals that become bored, despite being peanut brained.
I would add a few large objects, even old junk like kid's wagon or dog kennel, to the runs, to break up the space and create more private areas (but make sure to have way in and out of every corner you create). Add multiple perches and concrete blocks to create activity at different levels, toss in flakes of alfalfa hay to tear apart and forage, hide scratch under layers of hay so they have a mission, hang cabbages or toss in large cabbage leaves or whole apples that take some work to dissemble, add piles of leaves or yard debris, low tubs of water for wading, raised bed wire-covered chicken salad bars, cut branches with leaves on them to create complexity or any nontoxic natural elements for them to peck at, tear apart, and explore--so many great ideas here on the BYC--and let your imagination be your guide.
Good luck.