That solved it.
Syclone1, Thank you! Your tip reminded me that I needed to go into the properties dialog of the VraySpawner Service and set the Log On to my local admin account, but also set the Recovery to restart the service after the first two failures.
Now all slaves in the farm are running with registered services and are handling the water sim fast. They restart automatically after machine restarts without having to go into each one to launch the spawner application.
Edit: Now also a backburner job is processing the water sim with DR working very well on all slaves. All is well.
