Are the management interfaces of the ESXi hosts on the same subnet as the Windows servers?
What are the ESXi management interface IP addresses and subnet masks?
What are the windows server IP addresses and subnet masks?
Can the two windows servers ping each other, a windows server on ESXi host 2 does not need to be able to ping ESXi host 1 to be able to communicate with a windows server running on ESXi host 1.