Hi,I’m wondering if anyone can help on an issue i have with a stain on a porcelain tile,After grouting & the clean up a bucket was left on the floor overnight & the next day when removed the stain appeared underneath.I have tried with water a few times with no success & have left it over the weekend to see if it would dry out as thought it could of been trapped moisture but to no avail.I have enclosed a picture.Msny thanks for any advice.