Ryan - always state your RV year and model number with every post to get the best feedback.
Edit: never mind…I see your RV in the post description…sorry about that. Looking at your floor plan - the most likely culprit would be the bathroom sink. Look again under the cabinet, reach up and feel the connections and see if you find leaks in the supply connections or the drain lines. Are you the first owner?
Edit 2: if you were using the black tank flush when you noticed the water - the vacuum breaker valves on the flush plumbing system are notorious for leaking. Sometimes they are tough to find but they generally put an access hatch for access or they can be found behind the basement bulkhead walls.
MikenDebbie Aggie ‘77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy