I suggest the following for maximum availability and minimum issues:
a. Put primary on standby and make one of the backups as active while trying to minimize amount of changes in active member while doing the procedure.
b. Install on primary first.
c. Change the active member back to the primary
d. install on backups
As Emma said, there won't be sync while in different JHF versions, this is why we need to minimize changes, and when re-syncing use the SMS with the more updated DB if any changes.
Also, I don't know if you have such configurations or other dedicated servers but I suggest to distribute the logging between the servers.
Kind regards, Amir Senn