I have access to Kibana version 7.3
From this GUI is there a way I can confirm which elasticsearch version it is on? I cannot assume that both components are running the same version.
See question above.
You can use the following API to get all nodes versions
GET _cat/nodes?v&h=ip,name,version,name,jdk
the output will be like the following picture
For more information and more options you can refer the following page: https://www.elastic.co/guide/en/elasticsearch/reference/current/cat-nodes.html#cat-nodes-api-ex-headings