ive had this problem, like their saying seperate them, and they will heal up... chickens are rough on eachother when one bleeds their like "OWH shiny!!" and go after it!
Well, ive been at this for two years, and seen many chicks die of different causes, but to me a decapitated chick, sounds like a possum got a hold of her.. i mean true a new egg was their but another could of kicked ms. Broody off the nest the mr. oppossum scared the 2nd one and possums are WELL...