Hey guys, would like to seek advice from any sifu here. I forgot to take photo of the tiles, hence cant show you here.

The renovation of my house has just completed. I realized there were some small black and yellow stain on the tiles after the renovation. I have tried with vinegar, thinner, washing powder and water by using cloth, brush, and scraper but none of them could remove the stain.

May I know what these stains are? and how do I remove them?