WELCOME TO BACKYARD CHICKENS........I'M NEW HERE TOO. I HAD A HEN EXPERIENCING THE SAME THING YOU MENTIONED. I WENT TO TRACTOR SUPPLY AND BOUGHT A PACKAGE OF "FEATHER FINISHER" MY HEN LOOKED BETTER IN JUST A MATTER OF DAYS. HOWEVER, IF THERE IS A VIRUS OR SOME MEDICAL READSON, I'M SURE SOMEONE HERE CAN HELP YOU.
GLAD YOU ARE HERE.
Put one gulp of ACV in to a gallon of their drinking water and this should clear it up in a week or so and if you add some mashed up hard boiled egg's to their feed this will also help as this is common in chickens ....... I do this several times a month just to maintain the chickens health as it has to do with a balanced intestinal tract some yogurt is also good for them for this but Apple Cider Vinegar is the over all way to cover all base's ......