I have a couple black Plymouths that are losing feathers. But everything I read said when molting it starts at the neck on down. But they are losing their tail feathers and then more around the back area and not so much the neck area. My Road Island and Comets are not losing feathers. They are all 16 mths. old. Is this part of molting or should I be concerned? I had to put them all on antibiotics 2 weeks ago for a week for respiratory inf. and now this last week gave them vitamins and electrolytes. Any help on questions would be a great help.