It looks like she has had her feathers picked by another bird. Can you check her skin for tiny bugs such as mites or lice. I would use poultry vitamins in her water. One earlier picture might have had what looks like lice eggs, which are tiny white to grey clumps at the bottom of the feather shaft. Sorry about losing your other birds, but there may be something serious going through your flock such as Mareks disease. I would recommend getting a necropsy performed on her if she dies. Contact your state vet for details. The bodies must be refrigerated in a plastic bag, but not frozen.