I have a polish chick that does that. its always laying down. but will go to the feeder and waterer to drink.
then go to the light and lay underneath the heat lamp.
its now 3 weeks old.
it could be a number of problems, people on another forum told me that there chicken did that and grew out of it.
other people told me to put electrolytes in the water.
I looked it up and it could be Rickets. a vitamin D deficiency. so the electrolytes contain vit d so that would be good for that problem
other people told me to medicate with antibiotics.
the first week i fed chick feed that was non medicated. I didn't read the bag. so second week i got medicated. so thats what i am feeding now. and added the electrolytes to the water.
my chick is doing ok right now. just waiting and seeing.
I hope other people can help you out more than I, but the electrolytes in the water was definitely a good choice for me.
heres my chick last week