Now that they have started laying, you should be fine to feed them the pellets also. My hens prefer the crumbles over pellets, so that is what they get

! And, yes the pecking order can be brutal sometimes and I intervene, cause it drives me nuts! They respond when I scold them, by stopping anyway. I also have a hen who is the sweetest and is on the very bottom of the hierarchy. I favor her and give her extra treats
From what I have learned on this site is that if blood is drawn, the main bully needs to be separated for awhile and then when she is allowed back, she may have lost a bit of her upper status. I had a hen who was mounting a few of my lower ranking ones and I think I stopped her from doing that by making her submit! You know how some hens automatically squat for you? She never did, but I make her when I see her and she has stopped acting like a rooster. Check to see if your bullies squat for you and if they don't, make them. See if that stops them from picking on the one hen.