This was a the NYC datacenter (again) which has been utter garbage. We've been notified by our upstream that it's being shut down next month so we'll be moving this.
The problem in your cases were you were affected hard by this was that your domains had both of their nameservers in the same datacenter.
For now I've rerouted all traffic, should kick in shortly.
Going forward, you should change your delegations so that you are not single-homed (one datacenter) - we're going to be running a process to identify all these domains and email those affected.
You can switch your delegations as follows:
ns3 (NYC) can be switched to ns2 (Zurich) or ns1 (Miami)
ns7 (NYC) can be switched to ns6.zoneedit.co.uk (San Jose) or ns5 (miami)
ns12 (NYC) can be switched to ns16 (which is also NYC, but it's a different DC)
Sorry about this guys, we're going to fix this situation.