Because your rig is new, you could have a water line fitting that is not properly connected. It may be dripping slowly and flowing down the floor into the compartments.
The other possibility is something that happened to me when I purchased a new 5th wheel a number years ago. When they pressure tested the water system, they did not properly drain/winterize it. At the dealer, it went through some freezing temperatures and water in a 90 elbow froze causing a small crack that then leaked causing water to pool in the belly pan.
What ever the cause, it is something that needs to be corrected before it causes damage that might be difficult to repair.