Maran hen is very sick...I need help

[DEBO]

One of my 6 month old chickens was found in the coop a few days ago on her side. She seems to only be able to stand on one leg and then topples over. The other leg is curled underneath her body. Its freezing cold here so they have been in an indoor heated coop most of the time for the last 2 months. They eat layer pellets, cracked corn, sunflower seeds, and oyster shells. She is one of 4 birds. I brought her in and she is in a box in the bathroom. I have been force feeding (although sometimes she takes from my hand) her eggs and melon and berries and water w crushed vitamins in it for 3 days now. Today she is keeping her eyes closed more than before and is opening her beak to inhale with every breath. This is new. I was hoping she would recover in the warmth with good food and care but she seems to be worsening. Any thoughts or suggestions? Thank you!

 

[Eggcessive]

Welcome to BYC. Was she vaccinated for Mareks disease? I would suspect that as a cause or she may have injured the leg. Her poor appetite and breathing difficulty are worrisome. Has there been any respiratory disease symptoms in the flock before? Mycoplasma synoviae is a type of chronic bone infection, and it sometimes has similar symptoms of CRD or mycoplasma. Here are some links with info on some of these disease:
http://extension.unh.edu/resources/files/Resource000791_Rep813.pdf
http://partnersah.vet.cornell.edu/avian-atlas/search/disease/502
http://www.thepoultrysite.com/diseaseinfo/99/mycoplasma-synoviae-infection-ms-infectious-synovitis