Pods of mediawiki-bruce deployment have been created the same time the IO and network traffic increased.
pods also have failed readiness probes:
Readiness probe failed: HTTP probe failed with statuscode: 503
I assume the deployment is trying to do a rolling update of the pods, as one pod has a newer mediawiki image specified:
jelto@kubestagemaster1001:~$ kubectl get pods -n ci -o=jsonpath='{range .items[*]}{"\n"}{.metadata.name}{":\t"}{range .spec.containers[*]}{.image}{" "}{end}{end}{"\n"}'
Suggestion: temporary scale down mediawiki-bruce deployment to 0 replicas and see if load on kubestage1001 reduces and other services are reachable again (like tiller).