Reporting leaked passwords in github repository

I have just found a handful of repositories on github that contain database passwords. I want to let the concerned parties know about this so that they can change their passwords and remove the password from the git history.

All of these repos look to be web sites built by web agencies for their clients. All the repos are under the same account, each repo refers to different web agencies.

I'm not sure how I should proceed. I don't think that I should just open issues, because this would just put more light on the issues.

How should I proceed?