First time chicken owner here! I've done quite a bit of research, but I seem to have a new question every week. A few weeks ago I bought 12 pullets that ranged from 2-3 weeks old, and instead of getting one breed I got four different breeds lol. I have 3 of each: barred rock, Rhode Island reds, black australorps, and gold sex links. From day one, the gold sex links were twice the size of the other chicks. I am not sure if they are older than the others, or if it is just the breed. They're all around 6 weeks now, and they have partially moved into their outdoor coop. I have noticed with the gold sex links that they have had trouble growing in their feathers on their underbellies and butts. They are pretty top-heavy and unbalanced, so instead of sleeping on roosts they tend to plop down on their bellies. This explains the stubby feathers on their bellies, but I didn't see why they would have none or only short ones on their bottoms and around their tails. I have noticed the other chickens pick at their feathers, but it seemed harmless when I caught them at it.
However, today I went out to the coop and noticed multiple chickens were all picking on one gold sex link in particular, and they had pecked so much as to draw blood. I know the sight of blood or red in general gets most chickens excited, and I didn't want the whole flock ganging up on her. The gold sex links are the calmest, most docile of the group, and they hardly bother the other chickens. Their only want in life is to camp out in front of the food bowl. They don't even peck at each other or the other chickens. All three of the gold sex links are together in their main box, while the rest of the chickens are down below in the fenced in area. All of them have pecked at feathers, but today was the first time I've seen blood. I want to give the injured one time to heal without her wound constantly being pecked at, but I'm afraid of isolating them more from the flock. There is no one culprit that I saw. Instead, most of the flock seemed to harass the gold sex links in equal parts. I do not want them thinking it's okay to peck out the feathers of the gold sex links, but I don't know how they'll learn that because the gold sex links don't stick up for themselves, they just walk away.
Any suggestions would be appreciated!