Hen losing weight, lethargic, comb darkening

[ChickiesInTheCity]

OK, final update: I found small roundworms in her latest poop. I've begun treatment immediately for the whole flock. Thank you for your help.

 

[Wyorp Rock]

OK, final update: I found small roundworms in her latest poop. I've begun treatment immediately for the whole flock. Thank you for your help.

Glad you figured it out.

You can use Safeguard liquid goat dewormer (Fenbendazole). Dose is 0.23ml per pound of weight given orally once, then repeated in 10 days to treat Roundworms.

Valbazen (Albendazole) could be used instead. Dose is 0.08ml per pound of weight given orally once, then repeated in 10 days.

https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/

 

[dawg53]

Her mouth and vent look normal. I wasn't able to get a picture of her poop. I will keep trying but for now, describe it. It was runny, and yellow brown. The grains were white, and looked a bit like chewed rice.

Since the grains were white in color and looked liked chewed rice, did you notice if they were moving very slowly? If so, they are tapeworm segments.
Just for your information; it's possible for birds to have a tapeworm infection and a roundworm infection at the same time.
Valbazen will take care of roundworms, but if in fact there are tapeworm segments, you will also need Equimax equine paste to eliminate the tapeworms.
First, make sure you thoroughly inspect her feces for those rice-like segments before dosing with Equimax.
I'd go ahead and dose her with the Valbazen and worm the rest of your birds while your at it. If one has them, most likely the others have them.