Lethargic, Diarrhea, Thin, Not Roosting, What's Wrong?

[6RandomBrownLayers]

Hey Guys,
So I have a Golden Comet hen that I've had since she was a chick, she's a little over two years old now, maybe two years and two months-ish. Anyway, I recently lost a chicken to what I assume was a fox attack as I've lost several birds to a fox(es) over the years, so I've kept the girls in the coops until I come home so I can make sure they're safe. About a week or two ago I noticed that one of my Golden Comets was in the wrong coop and sitting on the floor instead of on the roost. This troubled me because I had another hen do the same thing and she didn't leave the coop and died at most a week later. This hen on the other hand continues to go outside and forage for food with the other girls when I get home. She is rather lethargic and she doesn't really seem to be able to flap her wings if dropped, not violently or anything, after being held like the other girls. She also has a lot of poop on the feathers near her vent that looks like it's mostly liquid before drying but I never see any oozing out directly from her vent so I think it's diarrhea. Her poop also smells really foul, I know poop isn't supposed to smell good but hers seems especially smelly. She is much thinner than the other hens, I can very easily feel her breast bone from her crop all the way down. She has access to food and water all day, even in the coop. Today as I was doing yard work she was eating worms and spiders that I found in the rocks so she's not just not eating. The skin on her breastbone also seems very flaky. I've read some other stuff that sounded similar and it said worms, is that possible or likely? If it is worms, what are her chances of recovering? Do I need to worm the rest of my birds, even the ones in another coop?
Any help or insight would be greatly appreciated. I have also posted pics if they help at all. Thanks for any and all help!

Poopy butt




Breastbone exposed

 

[Eggcessive]

I would worm her with Valbazen or SafeGuard liquid goat wormer or horse paste. 1/2 ml of either one, and repeat in 10 days. Start her on a little buttermilk mixed in with her feed 3-4 days a week for probiotics. Vitamins would not hurt in the water. Coccidiosis can still occur in an older hen if they are on new ground, or new birds have recently been added. Corid or amprollium for 5 days will treat that. Offer her soft scrambled eggs, a little dry cat food, or ground meat for some extra protien, and watch to see that she doesn't get bullied away from food. After her vent area is cleaned up, you might check her for vent gleet which can cause the smelly poops and bare reddened skin with white patches. Here is a link to read: http://www.tillysnest.com/2012/12/vent-gleet-prevention-and-treatment.html

 

[DressageRider]

Any chance you remember how you treated this hen? We had one that sounds just like this. I swore she had sour crop and was improving but now we have two more with similar symptoms. I sent away a fecal sample today but don’t wanna wait too long to do something. One hand I wanna start antibiotics on everyone and another hand I wanna start probiotics instead. ‍ No new members to our flock but we did move a few months ago.