How to get health checks to work on Kubernetes load balancer

Hi, Please tell me how to get health checks to work on a load balancer which is used by Kubernetes. I am running DOs managed Kubernetes service and spawned a Load Balancer service which has created an external load balancer, however when I hit the IP via HTTP I get a 503 gateway. When I check the health statuses of the nodes, they appear down.

Any help would be much appreciated. This is my yml for the service:

apiVersion: v1
kind: Service
metadata:
  name: wordpress
  labels:
    app: wordpress
  annotations:
    service.beta.kubernetes.io/do-loadbalancer-protocol: "http"
    service.beta.kubernetes.io/do-loadbalancer-healthcheck-path: "/health"
spec:
  type: LoadBalancer
  externalTrafficPolicy: Local
  ports:
  # the port the service serves on
    - port: 80
  selector:
    app: wordpress
    tier: frontend