Where have you placed the probes for the thermostats? They should be taped directly on the heat source. For the rack with the flexwatt tape a probe directly on the heat tape in an area where the tub in that slot won't hit it. If its a pre made rack it should have grooves and or slots in the back going through to the inside back of one of the tub slots just for probe placement.

For the rack with the heat cable tape the probe directly to the cable.

Then you have to consider that there will be a difference between what you have it set at and what the hot spot inside that section of tub is. The heat is being diffused by the amount of material it has to travel through so you set the thermostat at whatever you need to set at to get the required readings inside the tub.

Those internal readings should also be taken with a probed thermometer or a temp gun in order to be sure you're getting accurate readings within a couple degrees.