My 4 chicks were purchased 2 weeks ago....one of them is suddenly acting real docile....compared to the other 3 ( 1 Rhode Island Red, 1 Barred Rock, one Silver Laced Wyandotte) which are very active in the coop outside. The one eats and drinks and poops, but real lethargic. She just peeps quietly and closes her eyes like she wants to go to sleep. What do you think is going on? The others are ravenous eaters and are on the move all the time...but the one seems sick, and does not stand erect and jump around like the others. She is not extending her neck like the others. Any ideas?