Thermostat question

The cavity tub is in the middle of the rack. I have a cavity tub for every rack. Now with any rack there is gonna be some flucuation from the top to the bottom but not alot. My vision racks seem to be the best as far as this issue. They hardly have any flucuation

I try the temp probes on the inside of a tub with no animal, set the way that you would set up the tub with a Reptile. Then Check your temps around the tubs with a temp gun.