Sorry, but the temp that came with the heat lamp is wrong. Their hot side should be between 90-92, and the cool side 80-82. You should get them separated asap, and get some belly heat on them.
Are you measuring temps at the bottom of the cage? Is there enough room for both to thermoregulate adequately? What are you measuring with?
I can uderstand that a $10 dollar tub, with a heat mat and dimmer, can get expensive, but is it worth the risk of your snakes health?