@HeatherKellyB
I've heard "juvenile molt" referenced before, but I'm not sure what age this refers to.
Good question. As they grow in size chicks outgrow their feathers, so they replace them. Can you imagine how silly a grown chicken would look if it still had the same feathers it had at five weeks of age? These molts are called juvenile molts.
Some people seem to believe that every chicken in the world regardless of breed or mix of breeds or mutts, climate, time of year, how they are fed, or how they are otherwise managed go through juvenile molts at exactly the same age. That has not been my experience. Some go through these juvenile molts earlier, some later. I butcher my cockerels to eat, it is pretty easy to tell if feathers are growing back from a juvenile molt or not. From what I've seen most are over their juvenile molt by about 4 to 5 months of age. At 33 weeks that's not a juvenile molt.
As to when they go through their first adult molt. Some people seem to believe that every chicken in the world regardless of breeding, climate, time of year they were hatched, how they are fed, or how they are otherwise managed go through their first adult molt at a specific age. Again, that has not been my experience. Many pullets will skip the molt their first fall/winter and continue laying until the following fall, even if you don't extend lights. Some go through a full-fledged molt their first fall/winter. Some seem to go through partial or mini-molts.
The main driving force behind an adult molt is the days getting shorter. That's the one most of us thing about. But other things can cause a full molt or a mini-molt, usually some kind of stress. This can be at any time of the year and any age. Stress like running out of water for an extended period of time, adding or removing chickens so the pecking order changes, moving them to a new location or making changes to their current quarters, maybe a predator attack or some event that really stressed them. Broody hens have been known to molt out of season when raising chicks. Stress can cause them to stop laying for a while without molting but sometimes it starts a mini or full molt.
@WIMIke finally more to your questions.
Anytime I am petting another chicken she attacks that chicken as I am petting it. She also refuses to let me pet her at all.
Should I have separated the Blue Langshan from the flock or removed the Bossy Barred Rock
I don't pet and cuddle my chickens so I have not seen this type of behavior. I've had a chicken take a real dislike to another chicken to the point of trying to kill it. But I have not seen that to the point where they attack any or all other chickens. It's hard to know what is going on in that chicken's brain, that don't use the same logic we do. My guess, and this is only a guess, is that she sees you petting them so they are submitting to you. Since she is the dominant one they should only submit to her so when they submit to you they must be punished. Usually I'd expect her to be attacking you, not the other chickens, but they don't all always act the same. Each one is an individual.
I think some of the hens are looking thinner. Maybe not being allowed to go near the food by the Bossy one? Or is it possible for them to molt this time of the year in the cold
Again, I butcher chickens to eat. When you remove the feathers the actual body can be pretty small. Some more than others, especially thick feathered birds. When they molt and lose feathers they can look like they have lost a lot of weight when really is it only feathers. With feathers flying around and them looking thinned I'd think it is a molt.
Now, what to do. I try to solve for the peace of the flock, not for any one individual chicken. Since I eat mine I have an easy solution for girls as well as boys but you have other options. My first attempt would be to isolate that bossy hen for a week or so, no contact at all with the flock. When you bring her back she might change her ways. I have had some success and some failures with isolation. It's worth a try.
If the problem were only between two specific chickens I'd consider removing the other hen, not necessarily the boss. If everyone gets along great without her then she is probably the problem. I've done that before with success. It's not always easy to know where the problem is. With that other BR joining in the attack I'd think about this. But with that hen attacking other hens when you pet them I'd think she is the problem.
If separation doesn't work you can continue as you are. It's possible no one will be injured and they will eventually work it out. I think another option is to permanently keep them separated, build a second coop and run. Have two flocks. Or sell or give one of them away. Getting rid of one does not necessarily mean killing or eating it.
Your coop and run seem to be big enough. I don't see anything in how you are feeding them that would explain this behavior except you might try separate feeding and watering stations. Widely separated like one outside and one inside so she can't keep them away from both at the same time.
Good luck! These things are not always easy to resolve but a peaceful flock is a lot less stressful to you and the chickens.