there is one good product from Selleys which can whitening the toilet/ kitchen tiles easily. Dun know how to attach the photo here. The packaging is in tube form, something like toothpaste tube but bigger. The wordings on the tube is "Selleys White Stain Whitener". The tube colour is white and blue. I found this in Seletar Mall basement's hardware shops (not selfix). The shop next to Texas Chicken.