i have a simular situation in my setup. I have probes that are in each hide. then i have another dig thermometer sitting on the substrate in the middle of my cage. this reads about 85 F and it also gives me my humidity. I also have another probe that is hanging about 2 " off the substrate and is also near the center of the cage. same area as my dig thermo that reads 85 F and my probe reads around 78 F. so about 7 Degrees difference 2" off the substrate. My Bp seems to be doing fine, so i wouldnt worry about it.