corners wind blasted effect issue (2 replies)

Hi
I have built my first printer it is the prusa i3

I have an issue where when printing things like bumps on a print I get a wind blasted looking effect.
When I turn the speed right down I have noticed that my x axis starts its move a fraction of a second before the y axis has finished.
See the attached image.

I am using marlin firmware and repetier/slic3r software.
I have tried a lot of things to try and diagnose the issue such as adjusting belt tension, changing print speeds, adjusting layer height/width etc.
Nothing seams to make a difference.

Anyone have some advise of what I can try?

Cheers