According to HD Tune Pro, my SSD that I use for my OS drive is on death's door, it is a Samsung 840 EVO 120GB, and has written about 14TB in its life.
I ran a Crystal Disk Mark test on my 2TB Seagate SSHD, the drive was inactive other than the test:
Other drives in the system seem to show similar results, that are considerably lower than they should be.
As it stands, most other drives in my system are basically useless due to the speed; I know the SSD needs replacing at some point, but is that what would be causing the other drives to run so slowly?