Greetings fellow repti-lovers!

I recently brought home my first Balls (2)! Many years of wanting to finally came true. I did much reading/research before making the commitment, and had their home set up 48 hrs. before introducing them to it. Since then, the ambient air temp here has dropped and I am having a very hard time maintaining consistent temps in their habitat. I am able to get the warm side up to around 90 during the day, but I am very worried because it gets as low as 75 - 78 over night. The cool side seems to be more consistent at around 75 - 80 during the day, but has gotten down to as low as 73 over night. I am using a 75w basking lamp above the enclosure to warm it. However, to get the warm side up around 90 I have to move the lamp nervously close to screen. It seems like the utc heat pad just isn't cutting it, especially at night. I imagine that the substrate above the heat pad is a little warmer than the thermometer reads, but not that much. Please, any suggestions are welcomed. I am worried about my beautiful babies!