Water/moisture in Tail Lights

[Lakejumper]

I noticed that I am getting water in both of the tail lights on my Vista. This makes me wonder if the marker/clearance lights are also getting water inside. The screws are tightened as much as possible without cracking the plastic lense. I removed one and didn't see any rust or corrosion. Perhaps it takes more time as the Motorhome is a 2016 model. The lights on my towables all had caulking around them but these don't. Is everyone caulking theirs or or just leaving them alone? Aren't they supposed to be water tight? There aren't any slots at the bottom for draining.