Can you recreate it? An image showing the difference does not help.
The bug can easily be replicated by equipping three or more types of abilities/spawns/weapons/passives.that's literally it, it's just lower quality ability icons compared to the first three icons
EDIT: Bug has been fixed with the latest hotfix that also fixed the canvas editor bug.
I can only assume this issue has to do with ui scaling. All ability buttons use mip maps to keep the rendering quality smooth and become less detailed the smaller it gets. So, depending on the value you originally had might have caused it.