I have a 10 day old chick that is growing much slower than the other 7 I have. They're all the same age. All of them are very quiet and well behaved except one. The one had crusty butt a couple days ago that I took care of and she was silent and happy for a day but now is acting like she's in pain again. She makes noise constantly unless she's asleep and when I hold her I can feel her tense up or wince every now and then. She acts very needy and I don't know what she wants. She eats, drinks, and poops just fine, isn't cold or hot, but is much smaller than the other chicks. Here's a video of what she's doing and a picture of her next to the other chicks. I don't know if there is anything I should worry about or not. This is my first time raising chicks on my own so any advice is well appreciated.