To be clear, the above does not mean your server is running out of memory. It just means Erlang tooling for measuring memory/cpu usage has terminated, which will always be logged when Erlang shuts down.
So, without further evidence, all we know is that Erlang is shutting down. Do your logs say something else? Do you have metrics that say something else?
If it is a phoenix app, you can enable Phoenix.LiveDashboard, which may be easier to setup than observer: Phoenix.LiveDashboard — LiveDashboard v0.8.7
Open up the dashboard and you will be able to see if memory is growing, processes used, etc.
