i have a 13 day old plymouth barred rock chick that is half the size of my other chicks. the past few days i have noticed her off by herself generally lying down. today when i went to clean out the brooder i took all of the chicks out and put them in a seperate box and all of the other chicks stepped on her so i took her out and set her in my lap. she is very calm unike the other chicks when held and just kinda falls asleep in your hand. i had all of the chicks vaccinated for Mareks at the hatchery and have had the save a chick in their water from the day i got them, they are on Dumor chick starter/grower non medicated. i was able to give her water with some dissolved food through a dropper but i have no idea what is wrong with her. i currently have her seperated in the brooder with her own food and water so she does not have to compete for it. any advice would be great. thank you.