Exchange backup taking to long.

I wonder is somebody can help me, (my knowledge of Backup Exec is limited) our backups recently have been taking hours to complete, what normally takes 3 hours is now taking up to 11.
I have checked for updates and made sure there is plenty of space on the Qnap drives it writes to. I have also checked the alert notifications and nothing is showing untoward.

Can somebody give me some advice and steps I can take to resolve this?

Many Thanks in advance.