White residue

[P.W]

Anyone know what the source of this might be? It won't wipe off with soapy water and a microfiber cloth.

I've read about using a toothpick to scrape this off but would rather learn the possible source.

Wearer has not worn lotions, etc.

[bellagorilla]

Have you used it in a pool lately?

The picture won't enlarge, but it looks similar to the way my watch looks after a few days of practice and showers without a good cleaning.

[P.W]

Sorry here is a better photo.

It's my son's InspireHR. Not been near any pools. A toothpick has scraped off the residue from the screen.