My Serama hen is not eating or drinking, seems sick. Please help

[sickchickenhelp]

My 6 month old Serama hen has been sick for the past few days and isn't getting better. She is not eating or drinking and is lethargic. Her comb is turning darker and the feathers on the back of her head and neck are gone. Her poop is VERY smelly and liquid. She is also having problems walking on one of her legs. She has not been laying eggs while sick.
We thought she had puttybutt and gave her multiple sitz baths 7 days ago. Her vent was blocked and raw, but she has not gotten better since then. We have been making her drink electrolyte water. She seemed to be getting better, but not she seems bad again. This is one of our 3 chickens that we have and we are keeping her quarantined from the rest. We have never had a sick chicken and don't know how we would treat this.
Any help is very much appreciated.

 

[Eggcessive]

Welcome to BYC. Was she vaccinated for Mareks disease? Were her head and neck feathers pecked out by the other chickens? I would separate her, and bring her inside to rest her leg. Has she been wormed? I would begin by treating her for possible coccidiosis with Corid (amprollium) for 5 -7 days in her water. Then I would give her several days of vitamins with probiotics to get her gut bacteria and vitamins built up. And lastly I would worm her with Valbazen or SafeGuard Liquid Goat Wormer 1/2 ml given by mouth, and repeated in 10 days. Could she have injured her leg jumping off a roost? Mareks disease can cause paralysis in a leg or wing, or in the neck. It can affect chickens this age, and may cause a lack of immunity to many common diseases. I would explore all possibilities with her leg since it is probably an injury, but here are some links to read about Mareks:
http://extension.unh.edu/resources/files/Resource000791_Rep813.pdf
https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq
http://partnersah.vet.cornell.edu/avian-atlas/#/disease/Marek's_Disease

 

[myfinefeatheredfriends]

Do you have a rooster? Could it be possible that a rooster was a little rough with her, hence the missing head/neck feathers and the injured leg? If so I would keep her away from him for at least 2 weeks to give the leg time to heal. The neck feathers, with a rooster around, will probably not grow back in, especially if she is his favorite hen. As the post above says, it is possible she has Marek's Disease, but if so, I don't think the vaccine will work at this late in age. The vaccine must be administered to the hen as a day old chick for it to be most effective. Marek's Disease can cause a bird to have good days and bad until the disease progresses enough to take the hen's life. I hope this isn't what she has but it is a possibility if she was not vaccinated at hatch. Good luck to you and here's to hoping your little girl feels better!