Hi Jonathan,
I tested this and for me if I add a new node the indexes are getting replicated automatically after a couple of minutes. I was able to Explore them with only Exploration server running on new node. Your new node contains a Master server as well?
Out of the 5 I had only one gave me trouble, some EOF error (was fine after re-indeixing using new node Indexing server). I suggest you open a new message with us and we'll take a look at your environment.