Worried about much smaller chick

[chicksACK]

My babies were 3 weeks old on Monday and one of my lavender orpingtons is half the size of the rest of the group. She is eating and drinking does come over to me when I put my hand inside but she is laying down a lot and under the heat where the rest are not. The room they are in is around 80 degrees plus they still have heat available. Anything I should be concerned about this is my first batch of babies I have had them since they were a day old.

 

[Mountain Peeps]

Chicks grow at their own speed and rate. Has she had any issues prior to this that might halt her growth? I had a sebright once who had a very bad case of pasty butt and she was always smaller than the others and grew slower. Just make sure they are warm and have plenty of water and food.

 

[chicksACK]

My chicks will be 5 wks tomorrow and the littlest one is still so small and she lays down a lot, she seems weak but is still in the middle of what is going on. I am just worried there is something wrong with her. I know there is not much I can do, but if anyone has any suggestions I would greatly appreciate any help. She picks but is not the best eater in the group, she has had no known health issues (first time raising babies) she also seems to walk a little funny