Haha, I know the feeling!
Many tangs can slightly change color and get white spots in certain lighting or when stressed. My Blonde Naso scared me half to death the first night I put her in the tank with the way she could change coloring. She still does it when the lighting changes.
I would just keep observing. It could be just stress/new environment, ich, change in lighting, etc.
If you can, which will probably be close to impossible, take some pictures.