Originally Posted by clutch
It could be that the grey water tank isn't sealed and some water has run out from where the pipe enters the tank. That water could travel across the tank and run across the fabric or plastic under the belly of the trailer to a place where it can run out.
I have a StarCraft 235fb, it is almost identical to your Jayco 22fb, except it has the shower on the curb side of the bathroom. I think Clutch's explanation here is probably on the mark. Especially since it seems that the water is dripping from the foam. My guess is that the tank has backed up your drain system where there isn't a tight seal, and is just leaking onto your belly cover, and then finding the way out via the lowest point.
I'd pull the coroplast down, dry it out, and then you have a couple of choices.
If you want to find out exactly where the leak is coming from, refill your gray tank to overflowing and look for the leaking junction while the belly cover is off.
Or, just assume that you will not have a problem if you never overfill the gray tank again.