Low resolution album art problem (on USB)

Whenever I load album art into rekordbox it is very low resolution eventhough the original image is proper quality. This issue is only when I want to put album art on the USB. adding it to local tracks does not have the issue.

Now the album art looks really shitty on my XDJ-XZ. (And in rekordbox on m Mac).

What can I do to improve this?