Help! What is wrong with my BR?

[Sharwig]

I have a Barred Rock that has pretty much lost all her feathers and her skin is bright red and warm to the touch. At first we thought maybe she was molting but she's been like this for at least a couple of months and seems to be getting worse, not better. Because of the stress, she's developed a good case of worms which we started treatment for. She otherwise seems healthy; eating, drinking, running around like normal. I've spent hours watching our flock of 8 and haven't noticed anyone pecking at her. Any idea what is wrong or how to treat? I took this pic last night after giving her an epsom salt bath and she's now sporting a lovely saddle to protect her bare skin.

 

[Poultry parent]

Have you checked for lice, and mites?

 

[Sharwig]

Yes, we check our birds regularly for them and have seen no signs of anything like that...and none of the other hens seem to be affected. We've tried no-peck solution, treating for vent gleet, etc, but nothing seems to help her. As mentioned above, we gave her a bath in epsom salt yesterday (she loved it!) and I put a saddle on her back to discourage pecking if that's the problem, but I really don't think it is. She still lays a couple times a week, but not consistently. Any other ideas?