So because the room you have them kept in isnt air conditioned or a "controlled" temperature it could likely be the cause. try to set them up in a place that has little to no fluctuations in temp so it is easier to control the cage's temps.

and temp "gun" i am guessing you mean the laser ones only do surface temps. get a simple air based thermometer. or http://www.reptilesupply.com/product...roducts_id=655 so you can get max/min readings and monitor it better.