I am new to raising chickens. My 10 babies are two weeks old and one of them started becoming listless today. Not eating, drinking, sleeping alot. leaning to one side. Tail feathers tucked under, wings droopy, chest feathers seem puffed out. Vent looks clear, tried wiping anyway with lukewarm water and afterwards looked like she was pulsing or trying to push something out! We tried to encourage her with some water but she vomited straight after. We have put her in quarantine meantime with her own food and water and clean litter. Have been feeding them chick mash only. She looks smaller than the rest, but not being bullied as the rest don't take much interest. I'm not sure what is wrong, but if anyone has any suggestions I would be most greatful.