I have a black/red hybrid hen and she is missing feathers from parts of lower back,Lots of feathers from the tail and some from the breast? i am pretty sure it is her getting pecked on! I have been told to remove her WHAT SHOULD I DO!
If you think she's being picked on, remove her from the other chickens. Put her in a dog kennel or her own run to assure she's safe. Look into rehoming the mean birds or your picked on hen or deal with the separation and get her a friend.
Removeing her could work but you could also just watch and observe your flock. They could be pecking her for plenty of reasons. They might be fighting over something and if that's the case just remove whatever they're fighting over or get more of them. I am new too and am not very experianced so I could be wrong that is just my opinion. Good luck with your flock!