ext4 FS theoretical limits vs actual limits

I've got a box here that has a 2TB FS across two 1TB disks (~1.8TB usable space after LVM and ext4)

It's currently holding around 1.4TB of data. I'm finding that it's corrupting a lot and performance has dropped significantly.

Have I gone over the recommended size limit? Should I just cut my losses and separate the space?

EDIT: I've found it's 7.4% contiguous, but that's barely a scratch in the surface - shouldn't be too bad.

The actual cause is bad sectors on the drive. I'd apologise about posting such a useless question, but it was posting the question which got me thinking to check the drive's health.