I tried to ping Sonic's DNS servers and did not receive a response. I also tried Google's 18.104.22.168 and also received no response.
Approximately 5 minutes later, the DNS servers became responsive again. Was there any network maintenance performed this morning? Sonic's MOTD doesn't show anything for today.
Over the past couple of months, this issue has shown up before at other various times - 8:30 PM, 10:00 PM.