Kibana: No Living connections

I have built a distributed Logstash environment with 2 Logstash/Redis servers, 3 ES nodes, and 1 Kibana server.

I have made the recommended performance changes to the ES servers (ES Heap, Max file, etc). And my ES environment seems stable. However, I am getting "Fatal Error: Kibana: No living connections" on the Kibana server UI. If I restart the ES process on the three ES nodes, it seems to clear this issue, but then it comes back again in about 15 minutes.

Do I need to apply the ES performance changes to the Logstash and Kibana servers as well? They are part of the cluster but are not data or management nodes.

Is there something else I need to configure?

What KB version?

Kibana 4.0.2, Elasticsearch 1.5.0, and Logstash 1.4.2