Your best bet, at this point, would be to do the following:
1) Go to the Seagate site and download their drive health utility
2) Run that utility against each of the drives
3) If it shows either drive as failing, then start the process of contacting Seagate to have the drives replaced under warranty

The sooner you do this, the better.

Only telling you this because I had a Seagate 3TB go from unreliable to totally failed inside a week. Every day you continue to use these drives, you're risking total failure of the drives.