Sick Hen. Thin, Dull feathers, lethargic not eating

[Julie in Maine]

So she has a discharge from her vent?
Poop that I have seen like that with my hens, they had a reproductive problem. Peritonitis and/or cancer.
Yours may have something else going on, a yeast infection. If so, then I would give her the monistat orally, but give about 1/2 inch of the cream. You can also treat with Nystatin if you can find it.

 

[Julie in Maine]

poo looks good this am. She is still puffed up, but eating better. Will keep at this a couple more days!