Tank Heating Struggle

[Olivia13]

Hello,

First time reptile owner and I've had my baby corn snake for about a week and a half. I should note she ate on Wednesday, and has since pooped and I found a urate.

I've been struggling with heating since day one. I live in New England and its pretty chilly in my house. I have a UTH and a halogen bulb (25 watt). Since the beginning, she seemed to like hanging out at the top of the tank in a tree and even perched on the thermometer display. So I put a bamboo hide up at the top so she could hide and without worry about her following if the thermo suction cup fell. She has spent almost no time on the ground. She would sleep at the top all day and would come out to explore a little bit at the end of they day before i shut the lamp off. Recently I haven't seen her come down at all. the couple times I handled her she would hide in the substrate (cypress mulch) when I put her back but eventually would wind up back in her bamboo up top.

With that being said about her behavior, the temps in the tank (12x12x18 in exo terra) seem very low. I put a thermostat probe (set to about 90 f, can I maybe turn it up more? I don't want to burn her) for the UTH and a thermometer probe close to each other buried a little bit under the top of the substrate where I wanted her hot spot to be. The UTH is placed in the back left, and the lamp is in the front, centered. I put another thermometer probe similarly buried where I wanted her cool hide to be. I finally got a cheap Zoo Med Repti Temp Digital Infrared Thermometer and used it to check the surface temps and they seem really low, down to around 66 f. The thermometer probes usually read 80 on the warm side and 70-75 on the cool side, but that doesn't seem to match what the infrared says. At night with the lamp off it definitely gets cooler.

I'm very concerned about the fact that she does not seem to leave that bamboo hide I've placed at the top though maybe her active time has just shifted alter to when I'm in bed. But still she spends so much time where its probably the coldest spot at night. I read that you should see them move around to regulate. I tried to provide as much detail above to see if anyone has any advice for how to better heat it and let me know if her behavior is concerning. Open to any and all advice or info and can provide more info if it helps.

Thank you in advance!