It's very possible that they are just moulting, which begins around the head and neck. How old are they? If they're reaching or at laying age, probably moulting. Any signs of mites? If not, probably moulting. Are they low in the pecking order? If they are, it's possibly not moutling,
and could just be the other hens just picking at their feathers.
Hope this helps!
thanks..could be molting.. they were a year in May. I haven't noticed molting b/4... just thought it was weird..being just two of them and just on their necks. They are not the lowest on the totum pole.. thanks again