My first advice is to take the regulator to your LDS and have it checked out properly.
The most obvious, layman's, inspection of a regulator for water ingress is discoloration of the 1st stage filter and any signs on water inside the SPG. However, a reg can seem ok in these respects, but still be degraded.
If you suspect fresh water ingress, you can do a quick fix (maybe on liveaboards or remote sites) by removing the SPG...and then connecting to a tank. Slowly crank on the pressure and it 'can' blow any ingressed water out of the system. Not idea, and I am sure some on here will disagree, but it is a last ditch solution if you are not able to properly inspect/repair the regs yourself or get them to a service technician.