tl’dr? Set new database passwords and move to PHP7.
I just noticed all 3 of my WordPress blogs have been down for most of the day with a database connection error. It looks like my my MySQL database back-end was upgraded or modified overnight by my host and my MySQL ‘old_passwords’ were no longer valid.
The simple work around was to set new database passwords from the MySQL front end for each connection then update my sites config files with the new connection information.
This looked like it had worked at first, my sites came back up and all looked well again. However I soon found I was unable to access my WordPress sites back end control panels due to a 500 server error at the admin login page ‘\wp-admin\’. Looking at the WordPress logs I could see various initiation errors and out of memory errors. I took this opportunity to switch to PHP7 (coming from 5.6) and now everything is working again, I am not worried enough to go back and find out what the issue was there but have been looking at moving to PHP7 for a now and it seems like the logical place to be, and my host allows more memory if you use 7, great! 🙂