I have a 5 week old RIR that has developed the bad habit of picking and eating feathers. He is the only one out of eleven that will pick a tail feather and eat it. All the others seek out, scratch & peck just the food & black sunflower seeds. When watching this little guy in the pen, he wanders around, targets a tail, pulls a feather out, eats it, and then hunts for a different tail to pluck. I have separated him (he's in a pet carrier right now & very unhappy). He did this a week ago in another pen, so I isolated him and then put him in this pen with chicks that were a couple of weeks older than him. He was at the bottom of the pecking order and didn't feather pick at first. Now he's back to doing it again. Do I need to cull him?