Unload spot lights when tracker is out

I'm fairly new to Unity/Vuforia, so I might be missing something obvious here... please help :) In my one Unity scene there's one AR Camera and below it there are 5 imagetrackers. Each one has it's own FBX model plus one or two (spot/point)lights. This is what's up: When I hold up the five imagemarkers when playing the scene the FBX models show up fine.  They of course disappear when I move the trackers away from the webcam, but the lights don't seem to unload.  When I move in an 'old' tracker again into the webcam's view, the lights pop back to the tracked marker / FBX model. 

So here's my question: Is there a way to disable the lights when the marker is not tracked? This applies to all types of lights.  Thanks!