Sick hen, can't figure out what's wrong, help!

[mvh]

My 2 year-old EE is not acting normally. She is lethargic, and doesn't eat or drink, as far as I can tell. I noticed it first last night when she didn't run to get a treat, and isolated her this morning. I have tried to check her out, but found no evidence of any issues. Her crop seems empty and I see no evidence of mites or lice. She last laid an egg about 5 days ago. She just sits in place, with her head hunched down. I am assuming she is molting, and thus the feather loss. I have attached a couple of pictures.

 

[mvh]

I don't think she is egg-bound either, and her breathing seems normal. I have not seen her pass anything since I isolated her this morning, nor before that either. She did make it onto the roost last night, I picked her off it this morning. She is making no attempt to get on the roost in her isolation cell at all.