New rack system and heating issue

So I recently bought a new rack a 7 space 50qt that utilizes heat cable and has cut out spots for it. I set it up a few weeks ago and had some issues with my top rack being about 3 to 5 degrees colder on the hot side than the other rack (where I want my temps to be) all of the other racks are perfect in temperature. My top tub is also where my probe is which I know it’s not the best place for it and I don’t mind my top tub being vacant but I still want all my tubs to reflect the same temps. Any thoughts???