Sounds like your apps are no longer able to establish a direct remote connection to your server. Instead they’re depending on a Plex Relay – such indirect connections are limited to 1 Mbps (2 Mbps for Plex Pass members).
Best start looking into your remote access setup.
Even if you didn’t change anything on your side, there could be changes outside your control, e.g. your ISP placing you into a CGNAT setup (where your router is no longer accessible from the outside) or blocking the port used for your remote access setup / port forward.
If you’re using an automatic forwarding, try to create a manual port forward and configure your router/Plex accordingly. Afterwards, check if your router is visible on that port from outside your home network (you can do that using a service like canyouseeme.org) – it’s also a good option to verify that the public IP / WAN IP of your router, the public IP seen by Plex (remote access settings) and canyouseeme.org match.
