Those double dome fixtures are pretty useless. They trap heat and heat is the enemy of most any type bulb. I causes them to burn out prematurely. I would recommend replacing the fixture with a wide dome - like a 10.5" brooder lamp. The heat dissipates better but the reflector hood still directs most light and heat downward. A standard household incandescent flood is my bulb of choice for basking heat. I use 65 watt bulb and it gives plenty of heat for any basking area. I add additional fluorescent about 6000K to balance the ambient light. A UVB tube fluorescent is then added for about 5 hours midday for UVB and UVA. Since you are in Florida, you probably can get adequate UVB by giving your tortoise some outside time at least a few times a week, so UVB is not an issue for you. However, good UVA is very beneficial to your tortoise and a good UVB light gives off really good UVA as well. So I personally would always have one for good peak midday light in an indoor enclosure. I believe that is the best combination for daytime. Do not use any colored bulbs. For nighttime = A CHE on a thermostat to maintain your minimum of 80° in the coolest part of the enclosure will take care of heat at night with complete darkness. Your other bulbs during the day will provide all the heat you need and the CHE will not even kick on.
Put a 65 watt floodlight in and your Basking / heating problems are cured ! 
