Yeah, the rainstorm shouldn't have had any effect.
It does sound like the router is the cause, since the WiFi is still working for MRV.
It isn't clear if all the receivers are losing internet, or just those connected via WiFi.
Your router should have a factory reset button, which would be the next thing I'd suggest. Of course make sure you have the factory password before pressing the reset, as this step clears everything.
I wonder if it is possibly a heat issue with the router. THis version of the router is a flat version, meaning it lays flat on the surface. Other versions are vertically sitting which suggests that air flow is better for them than on flat. The router is a little over a year old, I wonder if it is starting to fail. FWIW, We notice video stuttering that was not there before as well, which I experienced with a Belkin router I had a year ago. That stopped when I bought the Cisco. And now it is happening again. So I wonder if I should think about replacing. ALso, what's a good one that is reliable and long lasting?