I have wired 8, 1 foot sections of 11 inch flew watt. Now that I have them on the rack 2 of the sections read about 5-8 degrees lower than the rest. Is this common? I know the ones on the bottom will run cooler (I usually put insulation underneath to help that out) but that seems like a huge swing in temps. This rack is suppose to be for adult balls and if I have the temp set at 91 and some are running at 83 its not going to work. Any suggestions?