Why is there such a large difference in scan times between these servers?

Below is a pic from the scan log on 4 of my servers. What would cause this HUGE difference in scan times? All 4 servers have similar or identical specs, roles, storage, and total number of files yet it takes literally, 100 times longer to complete a full system scan. They're all VMware VMs running SEP v12.1.6168.6000 and the entire infrastructure was basically idle when these scans took place (note they took place on different days as well).

http://imgur.com/LWu0ZrP

Where should I start looking to find out why this is happening so I can fix it?

Thanks,