I have a flock of 17 mostly healthy chickens. Originally I had a rooster a hen and three babies, then I got 7 chickens from a friend, 5 red sex links, and 2 white stars. They are great layers, friendly, but have always had feather loss on their backs-I'm not too worried about it but it really looks like it might be permanent. AND they are terribly scrawny. I feed them all the same thing and the others (the young ones I purchased after these seven) are beautiful, filled out, and just gorgeous chickens. What do I do to help them? I feed them plenty of layer crumbles, mixed with scratch daily, and lots of table goodies that we give them from what is leftover from our meals. They eat healthy, lay great, but just look terrible! What do I do??