Hen Always Standing, Not Eating nor Drinking

I have a 1 1/2 year old white Leghorn hen who has been an excellent layer. She is one of 12 hens who free range. On Friday everyone looked normal. On Saturday I let out the layers and went off to get stuff ready to butcher our meat birds. While I was doing that my daughter walked up to the coop to visit the chickens. She came back and said one of the white leghorns was laying down outside and her comb was kind of brown. I went to check her out and sure enough her comb was dark and starting to shrivel up. She was not very active at all so it was easy to grab her. My first thought was that she had poisoning from some moldy food the hens had gotten into. I gave her a dose of epsom salts and separated her. We watched her all day. At one point she sat down once, briefly, but since then she has always been standing. She briefly ate Saturday but hasn't since then. I don't think she has drunk any water except for what I've forced down her throat. She has liquid light yellow and white poop with a little pea green thrown in for color.

No worms that I've seen.
Stands 24/7 as far as I can tell.
Eyes are normal
Breathing normal (no snot, etc)
Crop feels totally empty
Can't feel an egg in her abdomen
Vent is clean despite the runs
Feathers look good
Comb is shriveling up quickly and is quite dark now
Waddles are still big and bright red
No eating or drinking - just stands there
Between last night and this morning she seems to be slowly sinking into herself as she stands there - her head and neck are going more and more into her back and chest, but her legs are keeping her up.
No injuries that I can see or feel
Everyone else seems fine; haven't had any other illnesses in a year (the other was poisoning from something they found outside)
Hasn't laid any eggs since being isolated

Looking online it sounds like maybe a broken egg in her, but I wanted to see what other people thought.

Thanks in advance!

 

I had looked at the worm chart and I just relooked. The closest would be the worms and/or egg peritonitis one. Not the same color but definitely the right "type." I've only ever used pumpkins and apple cider to deworm with. Since they do all free range (and eat enough nasty stuff! - dog poop ) I suppose it would be wise to use an actual dewormer. I just don't like using anything that has a withdrawal period.

I am well aware from 1st hand experience of animals dieing from having to many worms and being dewormed. Not fun!! Still, I'll give this hen a dose of dewormer... nothing else is working. Better than having her die without trying.

Thanks!