Do you have a IR temp gun? If not, what are you using? Using a probe thermometer or a stick on thermometer will not give an accurate temp of the hotspot from the lamp. If your only monitoring the ambient temps and your hot side is in the nineties I would bet your hotspot is over 100.

Like Sho said most of us here use a uth with a proper tstat. Using this method you can have a hotspot of 88-90 and keep the ambient temps at 78-80. The less heat you need to provide with a bulb the less humidity you kill.