connect: connection refused from kafka server (got this issue without any code changes)

Normal Created 43m (x3 over 46m) kubelet Created container kafka
Normal Started 43m (x3 over 46m) kubelet Started container kafka
Warning Unhealthy 21m (x26 over 45m) kubelet Readiness probe failed: dial tcp 10.244.0.68:9071: connect: connection refused
Warning BackOff 80s (x158 over 44m) kubelet Back-off restarting failed container

Events:

45m Normal Created pod/kafka-2 Created container kafka
45m Normal Started pod/kafka-2 Started container kafka
23m Warning Unhealthy pod/kafka-2 Readiness probe failed: dial tcp 10.244.0.69:9071: connect: connection refused
3m7s Warning BackOff pod/kafka-2 Back-off restarting failed container
48m Normal SuccessfulCreate kafka/kafka resource type *v1.StatefulSet successfully created
48m Warning CalculateExpectedPodCountFailed poddisruptionbudget/kafka Failed to calculate the number of expected pods: found no controllers for pod "kafka-0"
48m Warning CalculateExpectedPodCountFailed poddisruptionbudget/kafka Failed to calculate the number of expected pods: found no controllers for pod "kafka-1"
49m Normal SuccessfulCreate statefulset/kafka create Pod kafka-2 in StatefulSet kafka successful
49m Normal SuccessfulDelete statefulset/kafka delete Pod kafka-2 in StatefulSet kafka successful
49m Normal SuccessfulUpdate kafka/kafka resource type *v1.StatefulSet successfully updated
48m Warning CalculateExpectedPodCountFailed poddisruptionbudget/kafka Failed to calculate the number of expected pods: found no controllers for pod "kafka-2"
48m Normal SuccessfulCreate statefulset/kafka create Pod kafka-0 in StatefulSet kafka successful
48m Normal SuccessfulCreate statefulset/kafka create Pod kafka-1 in StatefulSet kafka successful
48m Normal SuccessfulCreate statefulset/kafka create Pod kafka-2 in StatefulSet kafka successful
22s Warning BackOff pod/ksqldb-1 Back-off restarting failed container
2m1s Warning BackOff pod/schemaregistry-0 Back-off restarting failed container

The issue provides only Kubernetes event output; start by collecting Kafka, ksqldb, and Schema Registry container logs and the configuration for the 9071 readiness probe. Confirm why the broker refuses the probe connection and capture a reproducible cause with verification steps as the definition of done.

Written by the indexing model from the issue text.