They don't need any light. They do need constant heat with a gradient (variance) of temperature through the enclosure. What are the temperatures in your enclosure? What Do you use to determine the temperatures ( temp gun, digital thermometer with probe, stick on wall thermometer) ? Most people use a form of heat other than a light such as a stick on heat pad on the bottom outside of a glass terrarium or flexwatt in an enclosure made of plastic.These require a thermostat to regulate the temps. What sort of environment are you supplying for the bp? Do you have hides? What sort of substrate do you use? If we understand what your set up is it would be easier to advise you in providing the proper temperature.