Port 53 open on WAN side

I checked the same 3 routers running firmware v6 today and NONE of them shows port 53 open for either TCP or UDP. I have no explanation. Maybe losing my mind. Maybe they were being scanned or DoS’d and shut down the port in self-defense? Will continue to check and if the port opens up again will take screen shots of the nmap report this time. Sorry for what appears to have been a false alarm.