The performance of my Time Capsule has massively degraded in the past few weeks. I connect by LAN from several iMacs and via wifi from my laptop. Backup up is now very slow and it can even take several minutes to simply access Time Machine. Navigating Time Machine is awfully slow and juddery. It never was before. As a test I copied a 480 MB file from 1 iMac to the other and this was achieved in about 10 seconds. If I copy the same file to my Time Machine disk on the same network it takes about 8 minutes. Why the slowdown and how can I fix it? Tried re-booting etc to no avail.