Sorry for your losses. With a draft free area and heat lamp they should be fine. Try rationing the food let them eat what they want in the day but take the food at night and only give them water. See if that cuts down on your losses. i did 27 and lost none of them with food rationing and letting them be a little bit cooler as they generate so much body heat. They will eat themselves to death. If they are eating day and night it is too much and their body is over stressed.