I'm sorry you are going through this. I had a feather picking/plucking issue and did a great deal of research on it. Feather picking/plucking is typically a precursor to cannibalism, so the treatment seems to be pretty much the same.
I agree, if you think you have one or more that are primarily the culprits, I would separate them and consider culling or rehoming. This type of behavior can be a learned behavior, and once even one starts it, others are likely to join in.
I would also eliminate EVERYTHING from their diet that is not high in protein for a couple of weeks. Leave the chicken feed, but do not feed anything that is not high in protein. I would feed them eggs, meat, cheese, yogurt, etc.
It sounds as though you do not free range them? You say they have plenty of space - is there grass in their run, or have they decimated it? If there is nothing growing in the run, add raked leaves, straw, something for them to scratch and pick through. Sprinkle what you feed them through out the run and coop litter to help keep them busy. You may consider a feed block or two. The goal is to re-focus their attention OFF of each other.
This is really a very difficult behavior to change once it has started, but I know several people who have had success. It does require a great deal of attention and effort though.
If you can cover the pecked/raw areas with pine tar, that may help. I slather it on rather thickly and it has helped. It is nasty to work with, but apparently tastes even nastier and the pecking stops when I've used it. Be sure to keep it on the areas they are pecking at for a couple of weeks.
I wish you the very best of luck. I know how frustrating and heart breaking this type of behavior in your flock can be.
Take care,
Penny