It's about the time that a lot of leos go into a slight brumation... I haven't quite seen one go fully into brumation, just a lot of slowing down on eating and being less active. As a matter of fact, about half my geckos are very inactive now as opposed to how they were a couple months ago. They are still eating, but a lot less than normal. I'm not at all worried though since they aren't losing any weight and are healthy.
My air temps where I live have recently been in the 50/60s in the day and around the 40s at night... as opposed to a 90 high and 60 low during the rest of the year. This is a MAJOR drop for them, so I'm sure it's what it is... I noticed though that in the past two days that I started turning the heater on in my room, they have been a lot more active, and have almost been more active as before when the temps weren't in the 40s at night. (Though here I am nice and toasty in my room then leaving my room to step out in a 40 degree hallway! lol)
You say it's a constant 74 degrees... are you sure it's still that in the middle of the night? Most homes do get colder even with our thermostats set at a certain temp. Geckos can definitely feel the night temp drop and known it's winter.