Snake seems sluggish

So in the last two days I noticed my snake seems more sluggish than normal. He ate fine on Sunday and I left him alone on Monday. But when I handled him on Tuesday and today he seems sluggish. When I pick him up his bottom half just dangles and seems limp, instead of curling up and wrapping around stuff like normal. I don't think there is anything physically wrong with him because he can still move if he wants to, and has the strength to dangle from his tail. After handling him longer he gets more active but he is not usually sluggish like this when I take him out. I also noticed that he has developed what looks like a dry patch on one of the large scales on his head. It looks like it could be a piece of stuck shed but it wasn't there before.

The temperature in his bin is 90 degrees on the hot spot with air temp of 76 degrees above the cold spot. Humidity is around 60%. This has not changed in weeks and he has been fine up until yesterday. So should I be concerned?

You need to leave him alone for 3-4 days to digest his food.

Has he pooped?

Yea he pooped a little over a week ago.

I may have identified the issue. For the last half week or so I have been turning down my apartment thermostat to 70 degrees at night to help me sleep and reduce my energy bill (which has almost tripled since I began turning up the heat in the apartment). This morning I checked the air temperature in the tub and it was only 71 degrees. So I am going to keep my apartment at 75 degrees until I can install a ceramic heat emitter on the tub to keep it warm without roasting me as well.