Missing feathers on neck

[fowlweather]

Hi all, I am new to raising chickens. I have five Old English Game Bantam (OEGB) chicks which are five weeks old. Today I noticed that one is missing feathers around the back of the neck. None of the other chicks seem to be missing any. I have been observing this afternoon to see if I could catch any of the others pulling the feathers out. But I have not been able to catch anyone in the act. I looked them over for any sign of a parasite but could not find anything of that sort either. The one which is missing the feathers is the smallest of the five but she seems to have no problem holding her own at the feeder. The area on the back of the neck is slightly reddened but not overly so. There are no cuts or anything of that sort. What do you think may be causing the loss of feathers? Should she be seperated from the rest of the group? Here are a couple of photos.
Thanks
Fowlweather

 

[Mahonri]

Most likely getting picked on.

But could have some NN or Turken genes in there.

 

[morninggloryhatchery]

He is probably getting picked on like the other person said. I had a Cochin Bantam in with my other chicks and he was getting picked on and lost all his back feathers. I had to put him in another pen and his feathers grew back and now is doing well. Good Luck with your bird!