That's not enough info for us to tell what is causing that. You need to find out what process is responsible for the excessive disk use. You can do that by examining the Disk tab in the Resource Monitor. (Link at the bottom of the Performance tab of the Task Manager.)
Honestly, if it were me, I would be frantically scanning everything for viruses. From your images, it seems a "svchost.exe" instance related to the network was responsible for this, and those kind of "background" processes are generally de-prioritized so they don't affect "foreground" activity. They shouldn't be making your system sluggish like this.