One possibility is that it appears that your downloads share (hard to tell exactly because of anonymizing) is set to use cache: yes (every moves from the cache drive to the array whenever mover runs), and files currently exist on all the drives except for disk 10. You would get far better performance from that share by relegating it exclusively to the cache drive (or use the array only for overflow [use cache: prefer])
Also, while you have dynamix ssd trim installed, in the period from Jan 1 - Jan 13, a trim never ran. Doesn't mean much by itself, but did you set a schedule for trim to run?