If there isn’t any other sickly signs, I’d hope it isn’t water belly then. If you have a syringe and feel comfortable you can always insert about 1/4 or 1/2 below the vent and to the right. If a dark liquid comes out then that’s it.
Is she light and can feel her bone protruding though underneath her (between her legs)? Is her face sunken in?
Sometimes with coccidiosis they will still eat and drink and empty as normal but the parasites eat and absorb any nutrition with leads to death.
1st pic is of her during her better days and the 2nd when it’s worse.
Currently have a bantam delaware hen. She’s currently almost 10 years old and for the past 3-4 years, she has had this yellow curd developing in her throat.
I would give her fishzole (metronidazole) tablets and it’d go away...