Hello.
In the SHVMPRD cluster the only host that connects is the host2 that has VMware ESXi 5.5.0 build-3248547 this is true?
You could check the SSL certificate on the only ESXi host that connects and then on the other ESXi hosts that do not connect. Please capture and paste your results, attached link.
Determining the expiry period of default SSL certificates of vCenter Server and ESX/ESXi (2015600)
https://kb.vmware.com/s/article/2015600