Mucus, sudden decline after recovering from cold

[2Fast2Curious]

We have a chicken who is sick.

Mucus in the eyes, nose, some open mouth breathing, she wasn't eating or drinking for a while but we gave her Tylen for 3 days and she began to eat and drink again. Yesterday she was doing really well, energetic. But this morning we found her on the floor of the coop, like she had fallen off the roost, and she suddenly seems too sick to eat or drink. She is breathing heavily, flops to one side.

She is a pet chicken, we want to do everything in our power to help her.

 

[Eggcessive]

Sorry about your chicken. She sounds like she has a respiratory disease such as infectious bronchitis, MG, or others. She could have developed a secondary infection or air sacculitis which can make them much more sick. Antibiotics such as Tylan, Gallimycin, and oxytetracycline can help with symptoms, but they can cure a chronic disease. Can she move both legs and wings? I would probaly separate her to a crate inside where you can keep her from infection the others, and watch her closely. If she doesn't make it, I would send her refrigerated body to your state vet for a necropsy, since you need to be aware of any carrier diseases that could affect the rest of your flock. Here is a link for state vets in the US, and a link about common diseases:
http://www.usaha.org/Portals/6/StateAnimalHealthOfficials.pdf
http://edis.ifas.ufl.edu/ps044