I have 3 week old chicks. All are fine except for one who never seems to want to stand. She is alert and healthy other than this. When I pick her up and set her back down she just kind of lays there, except her legs hold her up a little. I know she can walk because when I tap her legs she takes a few steps and remains standing but she doesn't run from my hand like the other chicks, she walks. Is this something to worry about or should I just let it go and see what happens?