First time buying chickens I bought from Feather Lovers. Long story short something happened with the Vaccine they were supposed to get. Down to 2 chickens left. They are Bielifelder and are about 9 months old and have been laying eggs almost everyday for the past month. This morning found this one at first not leaving the roost, then she came out and huddled on the ground. She was fine yesterday. I have her in the house now isolated and have given her an egg yoke mixed with poultry drench. She has taken a few bites of it. She is standing in the box, her feet seem normal but she isn't moving much. She seems more alert than her sister's. The only visible sign is a small amount of bright yellow from her bum. I am praying it is something besides Mareks.