Five of my twelve hens are starting to loose feathers on their bellies, from their crops to their vents. They are some of my older birds at one to two years old. I have checked all twelve thoroughly for any kind of parasites, and only found I tiny bit of lice on two of them (which I have now treated). I have read online that this is an effect of broodyness but only one is broody! Could the lice be causing this, is it feather picking, is it the pine shavings in their coops? I have no idea, please help!