People have lost their houses because heat lamps started fires too. :/Rinda, it quite possibly is too cold for them. They need to be fully feathered and the 2 younger groups probably aren't. Is there a way to put a heating pad underneath where they sleep? Like in a pillowcase or something so they don't get it dirty? I'd use a heat lamp but be very very careful to secure it in 2 places. People have lost their chicks when the heat lamp fell and burned everything up.