I can't really picture what you are describing and I don't know your skill level. If it where me, I'd drain the water tank first. I'd then search for the leaking point. If the water tank is under the bed on the RV floor, I'd remove the tank to clean and dry the area. It would also give a chance to inspect the tank and connections. If the tank needs repairing, there are kits available to repair most tanks. If not repairable, you'll have the dimensions to buy a replacement.
If it's a plumbing issue, removing the tank would also perhaps give easy access to the leak/problem. Home Depot would get a few trips. SharkBite fittings for PEX tubing would get purchased and used to make things whole again.