not really sure at all ..but it sounds a bit like heat stroke...try lifting the heat lamp up a bit , as long as there are no cold drafts they should be ok . Try to get some moisture into them with an eye dropper, just tiny amounts , and see how they go . Sorry can't help anymore than that , but I haven't come across that either . I never had them THAT warm though , that sounds too hot to me . When I kept chickens and hatched eggs with an incubator, I only used a light bulb to keep them warm ,60 watt in a big cardboard box. They all did fine never lost any due to cold , just keep drafts off of them .
May be something else that is causing it , but my first thoughts were they are too hot. Hope that helps a bit...
cheers
Russ