Viv Too Cold

[Noh]

I have a 40 gallon, bioactive tank for my california kingsnake. There are live plants, springtails, and isopods.

She is about a year old, 25-26 inches, the humidity is normal. The thermostat is set to 85 degrees.

The vivarium is too cold. The cold side is about 65-67^fahrenheit at any given time, and the warm side is about 75. Room temperature is about 65^F

There is a CHE and a heat pad. She is constantly smooshing herself against the glass where the heat pad is, and is not eating bc she is too cold. Given, the room is cold and the house does not have central air - no heating. Fine for humans, bad for the snake, tarantulas, and detrivores.

How do I make it warmer? I would have thought a CHE and heat pad combined would be enough.