To the real estate editor: An easy way to whiten mildew-stained grout and paint is with ordinary household liquid bleach.
Pour the bleach into a wide-mouthed container and then "paint" it on the tile with a large paintbrush. The grout should whiten in a few moments. Work rapidly and keep the area well ventilated.
I do not know if this will help Julia Bristow's problem, but it is certainly worth a try.
My husband and I enjoy your column very much. Mrs. Robert Hobbs Torrance, Calif.