I have a 2012 RGU. My outside lights are all LED's. They supposedly last forever. It would be quite unusual for many of them to go out simultaneously. One cause of multiple lights failing would be a voltage spike. LEDs cannot tolerate over voltage. I would trace for power starting with the hitch. You can cut away the caulk around the light and and remove it to access the wire nuts behind the lights. All of the right side lights are supplied by the same circuit. So, start with the most forward light assembly. If you have power, then you need to replace the entire unit. The light assembly used on mine are discontinued. You will need to locate replacements with the same mounting hole spacing. Remember to remove all of the residual caulk and re-caulk around the light assembly.