This is not a pecking order fight. The pecking order has long been settled. Problem rooster? Your partridge rock is not a rooster. Bullying? Any chicken can be a bully if they are with a weaker chicken but some can be more vicious than others. They are about 9 months old. They should be acting like mature chickens but some are slow to mature. Is that white EE laying eggs yet?My EE rooster has always mated with all my hens except one, my white EE. ..... Then one day I saw him catch up to her and pull out feather from her back. Then I saw him catch her and she finally submitted, he mounted her but instead of mating with her he just pecked her head and eventually let her go. I also noticed my partridge rock hen (also on the bottom of the pecking order) go after her once..... my daughter saw the rooster and my partridge rock going after her..... What are your thoughts? Peck order fighting? Problem rooster? Other issues?
I don't know what is going on. It sounds like she has always run from him since adolescence instead of submitting. It could have something to do with maturity levels, hers or his but both should be beyond that by now. She may not accept his dominance as flock master for whatever reasons and he is trying to beat her into submission. He may just not like her, I've seen that between two chickens before. Sometimes if a chicken is perceived as weak the others may try to run her out of the flock. A sick or injured chicken can attract predators so the instinctive reaction is to get her away from the flock. Sometimes they kill the weak ones because of that. Lots of different things could be going on. Your rock hen may be joining in just because she can and may be OK as long as he is not there as an instigator or she may be a problem. It's not that unusual for a hen very low in the pecking order to bully others even lower, as if she is jealous of her position and wants to make sure she doesn't get pushed even lower.
My suggestion is to observe the flock while she is healing and not there and see how peaceful the flock is. After she heals put her back with the flock but isolate him for a week or more away from the flock. See how peaceful the flock is without him. Then put him back with them and see what happens. Make your decisions on what you see happening, not what some stranger like me over the internet tells you will happen. I know it is pretty common on this forum to always blame the male, males are evil and always the cause of the problem, but I've been known to sometimes solve these problems by removing the girls, not the boys. Sometimes I do remove boys. I don't keep individual chickens, I keep a flock that has replaceable parts. My goal is to keep that flock as peaceful as I can.