In this case, Most probably your ElasticSearch dockers might be running out of ES_JAVA_OPTS Memory.
Check the ElasticSearch Docker log as root,
#docker logs --tail 100 -f [Doker-ID}
You can get the [Doker-ID} with #docker ps
Also check,
#curl -sS "localhost:9200/_cat/nodes?h=heap*&v"
If...