My EE's eat each other's tail feathers too. They beat up one pullet up so bad, they almost pecked down to her skull. I put Pick No More on her head and they stopped.
Do EE's sell well in your area? I've actually had some luck selling chicks. Several times I've sold 'em as itty bitty chicks for $5.00... not too bad when they haven't eaten a bunch of feed at only a few days old.
Stoopid chickens. Are they eating the feathers they are pulling out? That usually means they need more protein in their diet. If not, it's either boredom, overcrowding (unlikely by you) or them being a PITA.
I have no idea, honestly. Never had an issue with it with any of my other birds, and I honestly am happy to downsize by 3 birds and not troubleshoot. I know that sounds bad but.... That's how I feel about it. I've tried several breeds of birds and they're one of the ones I haven't been big on. I like my dorkings and dominiques. My cornish are kind of aggressive and crazy but maneagable. So those 3 stay. And our white orpingtons are fine. I'm over chicken breed experimenting, we'll keep and breed what we have and upgrade when we can to better quality of the 3 we like!
It doesn't sound bad at all. You have enough on your plate and I'm leaning towards them just being a PITA personally. I know you take good care of your livestock.