Without seeing a photo of the fresh water reservoir or the plumbing configuration, I will offer up an experience I had. I also had experienced a water leak at the floor of the fresh water tank and immediately I began to fear the worst, a crack in the tank. Fortunately, after a more detailed examination, it turned out that it was a fitting on the water line connection on the bottom of the tank had apparently vibrated loose. After tightening up the fitting, the leak problem was solved.
As I think most in the RV community can relate to, there are a lot of weird things happen when systems or components are subjected to the stresses and vibrations associated with driving these mobile houses over the highways.
Hope this helps and best of luck in solving your problem.