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I'd continue to give her 400IU Vitamin E and 1/4tablet B-Complex daily along with a little egg for the uptake of E.
It's hard to tell her age, so I'd feed her a quality Chick Starter or an All Flock feed. If she's laying eggs, provide oyster shell for her free choice. It's a good idea to provide Grit (Crushed Granite) free choice as well.
It's hard to tell anything about the mass that is on her back. Could you tell if it was a feather cyst, tumor or some type of injury?
The bloody mass needs to be cleaned well. You can use Saline, Chlorhexidine (Hibiclens) or Povidone Iodine. Trim feathers away from the wound/bloody mass so you can see if better (take some more photos once cleaned and trimmed). Apply triple antibiotic ointment to the mass. If she's picking at it, put an infant T-Shirt on her to keep her from picking at it.
If she's heavily infested with mites/lice, you can use a Permethrin based poultry dust to dust her all over to help get those under control. Most stores like TSC carries this year round. Put the dust in a sock and use it like a powder puff to dust her all over.
Mites, especially can suck the life out of a bird, so hopefully the vitamins and good nutrition will help.