Get a much shorter enclosure. All your heat and humidity is rising.
Switch to belly heat. The lamp is drying out the air.
Get two hides.

Read the caresheet and sticky titled, "Glass tank setup" or something like that.

Such low humidity can damage their lungs and lead to a respiratory infection. You can lift up their hide and hit them with a spray bottle during the days leading up to a shed. Just don't soak the substrate so bad it won't dry out. It could mold or rot.