I use 2 snake racks that are 3 1/2 foot tall. They both have 12" heat tape along the back of the rack in one long strip. The cords stick on the top of the rack. The first tub has heat of 88.0F and the lower you go the lower the temps. The bottom tub is 79.9F. So obviously this is a problem. Why would one end be colder then the other? I use a herpstat but it only comes with one probe and no option to add anymore. If I stick the props in the bottom tub the heat rises to 88.0F but then the top tub raises to 96.4F which is too hot. Why is this happening and how can I fix it? Any advice?