If you live close to where your rigs are, it is not a bad idea to check when something like this happens. Sometimes if the pool goes down your miners can get confused and fail to start back up.

Usually setting a backup pool or two solves the issue, however, I have still seen it happen once or twice.

Using teamviewer (or a similar application) is a great way to easily check if your rigs are hashing correctly or not remotely.

That said, everything was running fine for me today (other than the frozen graphs) so you should be fine too :]