Do You have an under tank heating pad? Belly heat is much better since they lay directly on it and it wont dry up the air like a bulb does. Humidity is also important.

I keep an oil filled heater in my snake room on a ranco thermostat to keep the ambient temps right where I want them. I would try to keep the night temps 78 at the lowest in the winter, 80 would be even better for younger snakes.