Windows 2012 DHCP cluster has been split - check your timeservers

This is the icon you definitely don't want to see on your DHCP console:




First, check your network connectivity with the partner server. If it has gone down previously the parner relationship should be restored automatically when it comes back.
Second, you likely have a time diff issue. Standardize your time setup on ALL your physical Windows servers (NOT just on your PDC emulator. No doubt. Trust me.) (and, therefore, time is getting ready on domain clients) with the following commands:

net stop w32time
w32tm /config /syncfromflags:manual /manualpeerlist:"1.pool.ntp.org,2.pool.ntp.org,3.pool.ntp.org,time-b.nist.gov"
w32tm /config /reliable:yes
net start w32time

No need to w32tm /resync after this. Time should be corrected immediately