I recently had to repair a few loose tiles in my bathtub stall area, and regrout around them. I followed the grout instructions and yet the grout cracked? Any ideas where I went wrong? The brand I used said nothing about misting, so I did not mist. The tub is our only one, so it had to be used daily but the tiles and grout were sealed in plastic to keep them dry during the prescribed drying time.