You might want to add stronger highlights to make it less blurry. And... well, the Flow of brushes in PS does have influence on making icons blurry if you don't know how to manage it. I think the Flow amount between 5-30 really needs a good management, unless you use a higher value. Use a better/higher contrast if you use low amount of Flow. Maybe this is not the reason for blurriness. You might have used Smudge tool for blending the brushes too much.