Your coach is a few years older than mine so I assume it has the gray pipe throughout, but more on that in a second. I had something similar happen. I had water in the plumbing bay and it seemed to be coming from the fresh water tank because the plywood floor was wet around the tank. I discovered that the copper pipe leading up to the shower drain was leaking and water was traveling down the outside of the pipe and deposing on top of the fresh water tank and winding up on the bay floor. Long story short. The elbow running up the the drain floor had a hole in it. Corrosion I assume. I plugged it with Silicon and that was it! I pray it never has to be replaced. Tearing up the tile floor is the only alternative.
The other thing is this gray pipe. I just replaced several feet of it and the connections with Pex. I had another leak behind the shower due to tired gaskets in the connections. That leaked into the plumbing bay in two places. One of which was also on top of the fresh water tank. Keep your eyes open for leaks at the gray pipe connections.
1995 Liberty XL
Chris & Sara Jo Behrens