Hi, Kristy. The first thing that I would suspect is that the problem might be under the floor and not in the bathroom. Older plumbers were known for cutting out large sections of joists and other structural parts of a house when adding new plumbing. This may last for a while but slowly parts of the house sink. When this happens, walls try to move but have to crack to do it. The bottom line is that if this is the situation, you will continue to have movement and cracks. Check this first and advise us what it looks like.