Pinless Peepers and aprons may help with the bullying, but it isn't a great solution long-term. The truth is your chickens are bored and need more space. If you can't add on to the current run consider rehoming 2-3 of the girls so the remaining hens have more room. Can you let them free range, at least for a couple hours a day? If not, try throwing weeds or grass clippings in the run to give them a chance to forage. You can give them a bucket of dirt so they can dust bathe. Possibly add some perches to the run if you can. They just need something enriching to do instead of sitting in the run all day.