Heidi is an 8-10 month old Red Star. Generally very friendly and happy-go-lucky. She laid an egg yesterday afternoon. This morning when I opened the coop the other girls came running out like usual and she just hung around on the roost. She finally made her way out, took a few steps and stopped. She is just standing, not walking or even sitting. I threw out some treats, right in front of her, she didn't even touch them (that's never happened before!). When I picked her up she didn't even squat! Her crop is empty and she hasn't eaten or drank anything this morning! There are no injuries or outward signs of illness, no sneezing or hanging her mouth open. Feathers are clean, eyes are bright. She is just lethargic! We only have 4 chickens in a small coop. The other 3 girls are acting normal today. It snowed earlier this week but has warmed up nicely into the 50's and 60's but it has been windy the last 2 days. They eat organic chicken feed (available 24/7). Treats are alfala sprouts (2-3 times a week), BOSS (daily), homemade yogurt (every 1-2 days) and, earlier this week, a head of lettuce (first time). They also have a flock block in the run that they were pecking at yesterday but usually they ignore it. Sand is used in their coop so they have 24/7 access to that. We are new to chickens and this is the first time that any of them have seemed off and it has me very worried!