bbvol wrote:
We purchased a 5-year old home with walk-in marble tile shower that has
developed small cracks between the tile walls and tile floor and also
vertically between the side and back walls. The areas were originally
grouted rather than caulked but I've been advised they should be
caulked. Do I need to remove the existing grout first? Also, any advice
on what's best to clean the marble around the joint before caulking?


There is colored sanded caulking available if it's sanded grout.
otherwise the standard tub and tile caulk in white. It wouldn't hurt to
scratch out at least some of the grout if possible.

Mix household detergent with a little water to make a paste cleaner. No
vinegar!