You shouldn't have to have Elasticsearch installed on the Kibana node for Marvel to work. If Kibana is set up correctly to to see the data, Marvel will inherit that setup from Kibana.
Do you remember if you happened to create any new mappings or templates around the time that Marvel stopped showing information that might be overriding the Marvel settings?
Also, do you have any custom configuration in the "marvel.agent" section of the elasticsearch.yml files in your nodes that you can share?
Finally, if you go to the '/marvel/api/v1/clusters' URL path after your Kibana host name in the browser (e.g http://localhost:5601/marvel/api/v1/clusters), and format the JSON response into a readable view, does that reveal any information that you can share, or might signal to you what the issue is?