Good questions!Show a pic of your brooder set up, please.
Video of chick would really help, up load to youtube or vimeo and then link here.
What is the temp(use a thermometer) on the floor under the lamp....
....and then at the far end of the brooder away from the lamp?
Were these chicks hatched by you, or purchased at a store or...?
What all, and how, exactly are you feeding them?
Have you been checking their butts for pasting?