With the release of vSphere 6 Update it, SSLv3 will be disabled on all your ESXi hosts, that means that VEEAM can no longer backup theese servers, because they use SSLv3, VEEAM states that they will release Veeam B&R V8 Update late september.
Read more and find a workaround here:
http://www.veeam.com/kb2063



