I didn't mention the possibility of coccidiosis as another possibility. That can make a chicken lethargic, too weak to stand up or walk, have hunched posture, refuse food, and have runny or bloody poops. Corid (amprollium) is the usual treatment for 5 days in the water. I think that pets and animals always tend to get sick when vacation time comes around. Maybe a family member or neighbor could keep her in a crate (with food and water) and look after her while you are gone. Here is the Mareks link: https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq