I have a mixed flock of 7 birds...all the same age +/- 3 weeks... One of my birds has been getting pecked on very, very bad...but only by 2 other birds....I kinda let it go as a normal "peeking order" thing until I noticed the back of her neck...a patch the size of a half dollar that looked like it was open muscle...no skin or feathers... I separated her and used some Blue Kote and she healed right up... I did notice that she had a really swollen foot...which was bumblefoot and I cut out the hard kernals and bandaged her up... I don't know if she had the bumblefoot before the peeking started or if it was because of her foot that the other chickens saw and easy target... The other 4 chickens don't do anything...just 2 mean ones...or really one mean on and her side kick... Anyway, I ended up isolating the bad chickens for a couple weeks while the bumblefoot healed but when I put them all back together the peeking started right back... the poor bird is a white leghorn but now her feathers are kinda dingy while the other leghorn stays clean white...washing her didn't clean the feathers...it's almost like the actual feather color is changing...I wonder if it's health related.