I have a chick who is at least 4 weeks old (unsure of exact age) that looks to be bald in spots and her feathers look a little different from the others in the flock (more sparse & some almost look greasy). We have a heat plate on at all times in the brooder but she chooses to walk around all day shivering. Is this normal? Should we do anything to help her feathers come in? Overall she is eating/drinking/acting normal. This is our first time raising chicks. Thanks in advance!