If you've got a nail polish smell, it HAD to have been stressed yeast. I mean, it's not the grain, or the hops. so, it has to be water or yeast. It's not the water, unless you have acetone in the water- so that makes it a yeast issue.
It's often due to high temperatures and slight oxidation, but plastic equipment can leach those flavors as well.
I'd double check any plastic in your brewery and eliminate it, and double check the fermentation temperature system you have.