This is a false sense of security any heat source can overheat, and even the so called preset UTH that are not supposed to go over a certain temp do go above the stated manufacturer temps depending on the ambient room temps. (Not hearsay I tested some myself)10. Do you use a thermostat to control temperatures?
No, we use a preset exoterra uht
You MUST buy a thermostat before the worse happens.
How damp do you keep the peat moss.8. What are you using as substrate? If it has depth, how deep is it?
1 inch of Peet moss
There are 2 possibilities here based on what you wrote you are either dealing with burn or scale rot.
Burn would due to the lack of t-stat
Scale rot would be due to the peat moss being kept too damp