From the sounds of it, it's a space issue or that red lamp, which they don't need. I'd give them plenty of deep litter, some good grit if you don't have any already, a good place to dust(nice and dry and you can buy a bag of clay at most any Lowe's for that...it's fine enough to serve as a good dusting medium), turn off that nasty heat lamp and maybe even give them a loose mineral free choice, like kelp meal, and possibly give them more protein....and I usually don't suggest that to folks, but in this case they just may need something extra.
Have you checked them good for mites or lice? I'd go out at night and take a bright light...look closely at the area around their vents to see if you see any tiny creepy crawlies.