This is my first year raising chickens. My buff orpingtons are almost a year old. Right around the first of the year they started pecking at the backside of the chicken at the bottom of the pecking order. Then it started to spread to other chickens. Someone suggested they might be bored, so I got them some toys. Someone suggested it might be mites, so I dusted them, cleaned out their pen and dusted the pen. Then in January I had a chicken up and die on me. A friend did an autopsy but nothing was found out of the ordinary. It has finally gotten warmer here, so they are now able to be outside almost every day. Now they look horrible. The pecking continues up their backs and on their necks. They seem pleasant enough but their egg production is very sporadic. Out of 10 birds, sometimes I get 9 and sometimes 5. Also, some of them have pasty butts. I have caught them and cut it off but it doesn't seem to totally clear it. I have 14 new chicks coming in two weeks, which I will not integrate into this flock for quite some time, but I'm afraid of ever integrating them if the other ones have something wrong. Any advice would be greatly appreciated.