Sudden Network Speed Drop

Typically I would transfer files to my server at about 60-80MB/s. Recently and all of a sudden the max I will see is 25MB/s. I have tried different computers and all run the same. I have a gigabit switch and tried swapping it out and also connecting both computers straight to the router with no effect. In WHS2011 I have the SMART add-in and all HDDs show green check marks. Any ideas on what to check to find the issue?

EDIT: I am running Stablebit DrivePool with 6 2TB HDDs. All are showing 80% full. Could this be the issue?

WHS2011:
Pentium E5200
ASUS P5N-T
3GB DDR2