Can you please let us know the exact build number of each ESXi host and also the exact message that you get regarding the CPU compatibility?
Surely - I am running ESXi 6.7 13644319 on all hosts in question. The message I get is: The target host does not support the virtual machine's current hardware requirements. Use a cluster with Enhanced vMotion Compatibility (EVC) enabled to create a uniform set of CPU features across the cluster, or use per-VM EVC for a consistent set of CPU features for a virtual machine and allow the virtual machine to be moved to a host capable of supporting that set of CPU features. See KB article 1003212 for cluster EVC information. com.vmware.vim.vmfeature.cpuid.mdclear
But of course I do have EVC enabled on each cluster configured for Sandy Bridge. The super weird part is that two of the hosts have E5-2650 v2 CPUs and even though they're the same, with the same ESXi build and same EVC mode, it reports the message above.
I have seen this before, but problem was related to Spectre/Meltdown patch not present in some hosts which was running different build numbers, but in your case build numbers are the same. In that case, I would check the BIOS settings and firmware version if are the same across all three hosts.