technically, unless you plan on breeding your temps should stay pretty consistant both day and night. you will naturally get a slight variation at night due to the drop in room temps, but I would say that an overall ambient air temp of 73 is too cold for ball pythons. I come up with 3 possible fixes ( but of coarse theses are not the only ways as im sure other people will offer good advice.) (1) Raise the room temp. were the enclosure is located with some sort of heater, (2) add another set of heat mats on the cool side to raise the temps of the cool side obviously you will need a thermostat with that or (3) buy a 3/4" thick round ceiling fan box (often called a pancake box in the trades) a porcelain lamp fixture , a length of heavy duty lamp cord and a plug end. mount the electrical box in the desired location , attach the lamp cord to the lamp fixture and attach the lamp fixture to the electrical box drill a 1/4" hole in the back of the enclosure fish the lamp cord through the hole and attach the plug end. plug into a thermostat. Add a night bulb ( probably about 50 or 75 watt ) You can make a bulb cover out of some 1/4"×1/4" hardware cloth and mount it over the bulb. this is probably the least expensive option of the 3. hope that helps?