3 master nodes all creating individual clusters

Hello, I have 3 master nodes all meant to be part of 1 cluster. I have added the nodes to the discovery.zen.ping.unicast.hosts field in the yml files. However, they are creating 3 separate clusters. How can I remove those clusters and join them to one?

This has been solved. Turns out we were using deprecated fields in the yml for version 7.2 must use other fields. Refer to:

https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-discovery-settings.html

AND

https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-discovery-bootstrap-cluster.html