Just putting a bead of calk around the light is only a temporary fix. In order to seal them correctly you need to remove each light, clean the area and the lights thoroughly, then seat them in a bed of butyl rubber or better yet use Eternabond double stick tape. After re mounting you can then put a small bead of butyl around the fixture. Do not calk the covers to the fixtures. No need to leave a path for the water to escape if you don't let any in.
Brian, Loretta & Daisy (Golden Retriever)
2008 Holiday Rambler Endeavor 40 PDQ , ISL 400
2014 Ford Explorer toad