corners wind blasted effect issue

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

May be worth trying a different slicer program. I just started using Cura, after using slic3r for months. It improved my print speed and made slight print improvements.

I agree with Cat. But you don't have to change which one you're using. You can use a different version of Slic3r. You can download newer and older versions. If you're slicing it in your host software, try opening Slic3r on it's own and export you gcode directly from it.