LB are currently facing a DDOS attack on their DNS servers. Below are the IP addresses which have been affected:
162.251.82.250
162.251.82.122
162.251.82.123
162.251.82.251
162.251.82.119
162.251.82.247
162.251.82.118
162.251.82.246
162.251.82.249
162.251.82.121
162.251.82.120
162.251.82.248
162.251.82.252
162.251.82.125
162.251.82.253
162.251.82.124
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.