Help!? my chicken is to young to molt but is loosing feathers on its head!

Okay, so I have 5 chickens, 3 Rhode island reds, a black sex link, and one which I forget the name of but its not important. One of the Rhode island reds ive noticed, about a week ago, has been loosing some feathers on its head, though not the actual stem part. I know about molting but its December ( I live in Arizona by the way ) and all my chickens are 8 months of age. Its only the head and a TINY bit of the neck, I do not have a rooster, none of the other chickens have it, and none of the other chickens have shown any aggression towards her.They were all raised together since 5 days old and I think it would be strange if one of them, or they all targeted her only if its a deficiency in calcium, we also give them crushed egg shells. Please Help!