Had you had any suspected unclean shutdowns or anything else that might indicate you should expect some errors? I notice that disk3 and disk6 indicate in their SMART information that they may have had connection issues at some point as they have non-zero values for the UDMA CRC attributes. This may be a red herring as since this attribute never resets to zero it could be quite an old issue. You might want to consider, however, running a check filesystem on the array drives to make sure none of them seem to have any current file system level corruption.
I also notice that you seem to have the regularly scheduled scan set to be correcting. It is normally recommended that this scan is set to be none-correcting so that you do not have a drive that is playing up inadvertently corrupting parity. You normally only want manually initiated scans to be set as correcting as that gives you a chance to look into why a scheduled scan is reporting errors before any changes are made to parity and only issuing correcting checks when you are confident there are no obvious hardware issues.