Could be anything ranging from stress to personalities. I had one chick out of the Littles who wasn't as energetic as the others. She also seemed to sleep more - either under the pad or as far away from it as she could get. It was like she couldn't decide if she was too warm or too cold. But she eventually came around and now I'm not sure which of the Light Brahmas she even was. Hope your little ones do the same thing after they become familiar with their new surroundings.