Those are actually hard water spots caused from calcium that is in your water supply.  This is commonly know as “hard water”.  The most common way to reduce the hardness/calcium in the water supply is to install a water softener on the incoming water supply to eliminate the calcium in the water.  If you already have a softener and you see this happening it may be time for service.
Contact Hydro Solutions today to find out how we can help eliminate those pesky spots!