Hello everyone. I've never worked with grout before and I a couple of pieces of tile in the tub/shower area where the grout has started to deteriorate and is a prime place for "vegetation", dark spots, to start growing between weekly cleanings. The deterioration is no more than half a tile width and maybe four or five locations altogether. Can the small section of grout be repaired successfully or would this be like pulling the loose end of the sweater in that cartoon we all remember from a kinder, gentler time and end up having to re-grout the entire tub before it's all over? Thanks for your thoughts!