Most of your signs point to molt. Your chickens are old enough to be entering their first molt. To determine if they are now molting, look carefully at all of the bald areas on each chicken. If you see uniform new pin feathers covering the areas, it's molt. Molt can begin as early as August and take until January to complete. Usually, the necks and butts are the first noticeable areas of molt, moving to wing pits and wings, then finishing with tail feathers. Examine all of these areas for pin feathers that look like pin cushions.
This isn't to say that some feather picking isn't also occurring. Often, pin feathers offer an attractive "snack" because of the blood in them. This can develop into a habit where both the owner of the feathers and her mates will pluck them out. This can retard the process of molting. Painting Blu-kote on the bald areas can camouflage the pink skin and pin feathers to make them less noticeable.
During molt, egg laying drops off and sometimes stops until after feather regrowth is completed. Feeding extra protein may be necessary when your feed is below 18% protein. My flock gets 20% protein feed but I still offer high grade animal protein during molt to augment their protein intake. Feather building requires a lot of protein.
To make sure you don't also have a coop mite issue, go out after dark and wipe a damp paper towel over the roosts. If you see red smears, you may have coop mites on top of everything else. They come out at night to suck blood from the chickens and can cause anemia and at the very least, irritated skin.
