If grout is in between 2 different materials, say between stone and tile or wall and tile, then the 2 different materials expand and contract at different rates. There's no way to avoid this and that's why caulk is used more often in these locations. If you have grout cracking and crumbling in other locations such as the middle of a run of tile, then it's possible it wasn't sealed? Cracking of grout is unavoidable, but it depends on how bad. I would try re-sealing and see how it goes.

Great answers Rebekah and bepsf!

Both are correct.....movement can be due to insufficient backing stiffness, thermal movement, damaged substrate or improperly laid tile......the proper solution is to address the cause.

Another common and often overlooked cause is simply the wrong grout was used in the specific application.(i.e. environment or the tile itself)..

All good and accurate comments! If you cannot address the underlying cause right now, you might try elastomeric grout caulk, which can be more forgiving in some applications. This will not, however, address a broken shower pan or leaky wall membranes. Proper construction is the best prevention.

Who is the manufacture of the light fixtures?

I've looked through our files for details on the light fixturess and unfortunately I was unable to locate specifics about these particular lights. We typically use local boutique lighting companies to find unique pieces such as these, and perhaps if you visited some local lighting stores in your area you will likely be able to find something similar for your home. Good luck!

I find this design rather cluttered for my taste, with too many disparate lights, hinges, tiles, reflections, mirrors, crystals, etc. I particularly feel the sinks are too crammed in against the shower half walls. It may be the photo but it looks like the right hand sink leg is almost up against the tub partially blocking tub entry, and one's view from the tub would be the drain under the adjacent sink. I'm not sure why the shower niche is so large and would be concerned it would just highlight more clutter when actually in use (better hidden in the half wall). The electrical outlets next to the wet sink and shower appear hazardous. Restful colors however.