My bad -- I missed the 8 weeks. They'd be in my garage, too. EVERYTHING will eat a bird that young.
Under 1 year = pullet. Over 1 year = hen. For boys, under 1 year = cockerel, over 1 year = rooster. I learned this on here; lots of folks haven't found it yet, so now you know. At 8 weeks, though, many would just say baby chicks; often we only HOPE they're pullets at that age!
Now I understand the heat lamp. I live essentially where you do, climate-wise. They're kind of on the line for heat; depends how well feathered they are, and since they'e been under heat, they're probably not fully feathered (they do feather faster if raised by broodies in the cold.)
I don't have heat on my babies and they're about 10 days old -- you'd be surprised how long they run around in that cold, like half an hour or an hour, before ducking under mama for a few minutes to get warm.
Probably the best thing to do would be start weaning them from heat. You don't need to buy a heat lamp at that age, just a hundred watt bulb will do. If you can, I'd give them the choice of running around away from it, and see how it goes.