LB are currently facing a DDOS attack on their DNS servers. Below are the IP addresses which have been affected:
In case your domains are using partially branded OrderBox Name servers or your fully branded Name Servers which are pointing to the above mentioned IPs, they may not resolve. Additionally, resource records within the Zone like A, MX, CNAME etc may not be fetched.
LB are working in coordination with the data centre to mitigate this attack as soon as possible. Please follow this thread for more information.