Turkey help needed

we added turkeys this spring to our homestead. they did fine all summer and are in the general pen with the rest of our poultry ducks and chickens. they sleep in their own area. However this fall the last 3 weeks in the morning we have found 3 * a dead turkey. Yes it is cooler up here we live in the adirondacks. Other then c mean a little sluggish they do not exhibit any other symptoms the rest of the flock 6 are all healthy without any problems. They are a heritage breed - chocolates and bourbon mixed. They currently do not have a heat source at night. Should I let them sleep with the chickens? They seem to want to. The chicken barn is warmer since we have a light in there we leave on and in the extreme cold we have a heat lamp. Alpine goats are also on the other side of this barn (they are separated by a wall). The other thought we had was to completely separate the turkeys from chickens and ducks so they can eat without worry. Although they do seem to be the dominant birds when it comes to feeding time.

None of those animals need heat and I'd avoid an all night light. They need a dark period every night.
Without a necropsy, there's no way to know what killed them. I'd be ready to send the next one that dies to the state poultry lab so you know what is going on without guessing.
If you're in the Adirondacks I guess that means you're in New York.
Cornell is one of the best in the country.
Animal Health Diagnostic Center
240 Farrier Road
College of Vet Med, Cornell University
Ithaca, New York 14853
Phone: 607-253-4271 Fax: 607-253-3943