VMware backups greatly slowed down

I've been running BE15 for a while and it started out good, but lately my VMware backups have drastically slowed down. It seems to be related to SQL and Exchange stores throwing up GRT errors:

The strange thing is that the error message doesn't match the error description, the server names are totally different. All VMs have the latest agent installed. I've seen a 400GB Differential backup go from 6hrs to 12hrs, with the only difference being the job now throws out these errors.

Anyone know what is going on here?

BE15(latest patches)
Server 2012