Maxing out DB connections

I have only logged in as one user on my Heroku instance, ran a few questions and saved one and yet Metabase has maxed out my connections on both Postgres (internal application) and Postgres (analytical):

The instance shut down earlier as my analytics had maxed out at 12. I haven’t used in a few hours and its gone down to 9…

Why is it doing this? What can I do to stop it?
Perhaps adjust the JDBC connection string for both dbs?

I was thinking it might be related to this but here its detailed that the stale connections are kept from 1-3 hours for performance but I (the only user right now) had been off the instance for 8 hours before I took these screens and one connection pool had been reduced from 12 to 8, the otherstayed the same.