@TAC57 Plex themselves had a data breech awhile ago, there Plex code had some bad malware in, infostealer. Workstations and Public Facing services should be in VLANs regardless.
Look at netstat but bare in mind that it will most likely be noisy, Monitor Wireshare and pfSense together to look at logs, I would recommend wiping the system completely and starting from scratch. Change all passwords, move Public Facing services into there own VLAN with strict firewall rules, TrueNAS should be in a Storage VLAN, Workstations in their own VLAN. Having a flat network with public facing services is the worst thing you can do.
Implement a IDS/IPS something like Snort or Suricata, pfblockerng with Geolocation blocking which are the things I would suggest implementing as well.
Check have i been pwned also.