You might want to check her for parasites. If she has mites she will suffer from anemia; worms will consume the nutrients in her gut. When I feed back eggs to my hens, I scramble them and stir in a good Tablespoon of Chili pepper flakes. Do that every few weeks, haven't noticed any worms in the poo. Speaking of poo, flax seed can cause loose stools for chickens (it is a noticeable difference).
She is young to be molting. I suspect part of the feather loss is she may be the rooster's favorite and he is breaking her feathers when he mounts her. The roosters will differ in the way the mount the hen, most tend to wear on the hens feather above the tail, often leaving just the downy feathers, but my recently deceased (**** dogs) rooster would stand higher on the hens backs damaging the feathers on the wings. My girls look rather ratty but aren't molting and already I am seeing regrowth after a week of no Buddy. She also can be the victim of feather picking, possibility indicated by the fact all the other girls are well feathered (she is their source of protein).
Your chickens are becoming sexually mature and the ratio of 7 hens for 1 rooster is a bit low. I suspect you will see your hens will looked well used rather quickly. I have found having 10+ hens per rooster prevents a lot of the wear and tear the girls get over a year.
You may want to give your overstressed hen a small high protein treat for just herself. Great way to make you her buddy. A couple ounces of yogurt, cheese, left over meat or cooked egg (great way to use the cracked egg or stained shell not suited for selling)