Ooooooh never noticed that. I didn't like the cleaning bit because the stains were kinda hard to spot so I never put any skill points in cleaning.
This made me think about the skills and upgrading them. I personally would like to be able to see what upgrades are available in each skill tree. Mainly because, at least for some of the skills (I haven't touched all of them), every level you gain is a different kind of buff.
But overall it isn't a big problem. Keep up the great work!