Is there any other light source in the train room? Is this a problem from years ago that you're just noticing now? Is there sunlight through a window at certain times of day, CFL or fluorescent bulbs nearby, etc? If it is just the Cree LED lights in the room, I'd say it's time for an email to Cree to ask them how much UV is created by their bulbs. It SHOULD be negligible, but you never know what they're doing to get the color temperature just right.