How to connect kibana to a specific elastic instance on docker custom bridge network?

Kibana tries to connect to ES 6.8.10 and complains it is incompatible. Am I missing any other explicit compose configuration to hint Kibana to connect to ES 7.9, or is there a Kibana environment variable that can be set to make this work? Thanks in advance for the inputs.

version: '3'
services:
elasticsearch:
  image: docker.elastic.co/elasticsearch/elasticsearch-oss:6.8.10
  container_name: elasticsearch68
  environment:
    - http.host=0.0.0.0
    - transport.host=localhost
    - network.host=0.0.0.0
    - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
  networks:
    - elastic
  ports:
    - 9200:9200
    - 9300:9300
elasticsearch79:
    image: docker.elastic.co/elasticsearch/elasticsearch-oss:7.9.1
    container_name: elasticsearch79
    networks:
      - elastic
    environment:
      - "discovery.type=single-node"
    ports:
      - 9201:9200
      - 9301:9300
kibana:
    image: docker.elastic.co/kibana/kibana-oss:7.9.1
    container_name: kibana
    networks:
      - elastic
    depends_on:
      - elasticsearch79
    environment:
      - "ELASTICSEARCH_URL=http://elasticsearch79:9200"
    ports:
      - 5601:5601

networks: elastic: name: elastic driver: bridge