Yes, the ambient is unfortunately 70. I don't have central heating so I do what I can with a space heater. : ( I really want to move, actually, so I can have a proper snake room.

They have belly heat. I've noticed that the back corner is usually the warmest spot (90-92) and the floor is 85-88. So I tell myself they have some gradient, even if the cool side is too cool. I know it should be warmer.

My rack is seven shelves tall. The probe is on the third shelf down, under the heat tape, so it's making contact. Both Vision and Sterilite tubs have paper towels, so that shouldn't be a factor in the disparity.

Btw, this problem tub is on the highest shelf, so you figure it would be warmest, right?? I figure this has got to be an insulation issue. The shelf is taller than the tub, so I have the tub's lid on. When I checked the 6 quart with added styrofoam it read 85, so that's an improvement but still not where I need it.