I received four chickens that were all hatched on the same day. I believe they are Wyandottes. One has just started laying eggs, while one of them seems to be a "runt." Her comb is still small and pink, she weighs considerably less than the others, and she often just wants to lay in the hen house. I'm very concerned about her. Is she just a runt that's taking longer to develop, or could it be something else? She seems fine otherwise.