SQL Server 2012/2014 insufficient memory available in the buffer pool
I don't think there's much mystery to the the errors occurring with SQL 2012 Standard as that edition only supports 64GB of memory.  Set your max server memory to 64GB and this error should disappear for your SQL 2012 instances.

As for SQL 2014 Standard Edition, the max server memory limit increased to 128GB, so I'll echo Sean Gallardy's question in the comments and ask what else you're running on that VM or if you've over-provisioned the VM host by accident?