I bought a temp gun to read the temps in my cage. It reads air temps and surface temps. When I point the surface temp says 91 to 92 but when it reads the air temp is says 75. I'm worried the temp is too low in his tank since the air temp says 75. My heat lamp is set to about 92 should I turn it up to get the air temp higher or is the temp okay since the surface temp says 92