Remote access – Grouping different versions of the kernel

After a bit of trial and error, I managed to group two OS X machines. The master is running Mathematica 9.0 and the secondary 11.0. Everything was fine, the remote control was

ssh -x -f -l nwalton treebeard.local "/ Applications / Mathematica
11.app/Contents/MacOS/WolframKernel "-mathlink -linkmode Connect 4
-name of the link & # 39;two& # 39; -subkernel -noinit

To get additional performance in the short term, I got a trial version of 11.3 on a third machine with the same remote command, save for host names and start

ssh -x -f -l install install.local "/ Applications / Mathematica
11.app/Contents/MacOS/WolframKernel "-mathlink -linkmode Connect 4
-name of the link & # 39;two& # 39; -subkernel -noinit

The third machine executes Mathematica standalone fine, but when I add it to the cluster, the master executes 9.0 reports

LaunchKernels :: forw: Version 9 of the kernel is newer than the master kernel. >>

The previous remote kernel is still activated as before.

What's going on? I am perplexed.