curl -XGET http://herd-monitor1.blah:9201/_cat/indices?v
health status index pri rep docs.count docs.deleted store.size pri.store.size
green open .marvel-es-1-2016.11.11 1 1 79 0 268.3kb 125.5kb
green open .kibana-monitor 1 1 3 0 64.1kb 32kb
green open .marvel-es-1-2016.11.10 1 1 7487 0 1.9mb 1001.7kb
It looks like something is not publishing the .marvel-es-data-1 index, which is mostly populated by your master node. Can you verify that Marvel is running on the elected master node? It is probably worthwhile to run
curl -XGET localhost:9200/_cat/plugins?v
(Edit: And I noticed your own response indicating that you found it)