My 2003 had such a leak and it was because airstream used a fill tube hose to the potable water tank that did'nt make a good seal and when I filled my tank the sloshing water leaked onto the floor, satuating the dinete and upto the sink area.
The hose looked like dryervent hose but smaller and it was clapped to a barbed fitting. I removed the dinette seat over the tank and discoverd the leak. It could also be comming in from around the potible water fill door if it was not sealed well and the rain was very heavy.
Good luck hope its that simple.