Need help on retaining the password set in pod

Hi community,
I am facing an issue in the Grafana deployment on Kubernetes. My deployment.yaml looks something like this(please ignore the indentation issue in the yaml config).

deployment.yaml-

I am setting the username and password for the adminuser login via a Secret and passing the credentials as environment variables. I am able to login into the Grafana instance with the username and password as set by me in the Secret. But if I change the admin password from the UI like this -

and I delete the Pod, my new instance comes up with the username and password as it is set in the Secret and it does not accept the password which I changed in the above step. How can I retain the password across Pod deletions?