For anyone interested, I have completed this and it is good. Following this guide https://www.jgranzow.com/?p=23 I created my CA and certificates I needed for my VCSA 6 and my 2 esxi 6 hosts. I downloaded the CA root crt + key and the host crt + key and uploaded all of them to a shared storage space. I followed this guide using option 1 https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2097936 and it asked for the VCSA crt, key and also the root crt. I then followed this guide https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2113926 for my 2 esxi 6 hosts starting at the "Installing and configuring the certificate on the ESXi host" I noticed I needed to remove the hosts 1 at a time from vcenter, update the cert, reboot the host to be on the safe side and re add back into vcenter. All certs are now trusted and good for 10 years.