loginwindow process using over 12GB of memory, system running ultra slow

This problem seems to have sprung up right around the time I updated to 10.14.6, but I can't be sure. Either way, my mac mini performance has slowed down to a crawl. Every single app runs slower. I looked in Activity Monitor the other day, and noticed that loginwindow process is using over 10GB of memory. I killed that process, let it crash out to login, and logged back in. Everything runs smoothly--the way it has for the last 4-6 months since I clean installed Mojave. But within a single day (and without any other apps being open), I came back to the computer and it takes a minute to log in and the loginwindow process is now at 12GB of memory usage. If I have more than one app open I start getting errors that I have run out of application memory. Does anyone have any idea what could be causing this and/or a potential solution? I'm willing to clean install everything, but I'm hoping to identify a cause before I reinstall all the same apps and potentially reintroduce the same problem. The main things that have helpers/assistants/daemons running at all times are Drobo Dashboard (DDAssist), Backblaze, Plex, and 1Password. I uninstalled Dropbox fully a day or so ago because that was my first suspect, but the problem is still unresolved.

Running 10.14.6 on a Mac Mini Late 2012 2.3 Ghz intel Core i7 and 16GB Ram