Thanks very much, Avanti and Mongo. I am being extremely careful not to let it squeeze up where the grout will go. I've already experienced having to chisel out thinset from the grout lines. That wasn't fun and it took a very long time. I'm dreading doing the grout. Not sure if I dare to try the Fusion grout that you suggested, Avanti. I don't want to get haze on the stones but it does seem that following the directions carefully would prevent that? I will seal before grouting. Is it a good idea to use a grout release over the sealer as well? I'm also considering Permacolor grout. It isn't available in our area so I would have to drive about an hour away to buy it. Not sure if that would be worth it.

The oddest indicator to me is your first photo, the sliver of "whiteness" on the floor along the wall in the left part of the photo. If that is truly there and not a photo anomaly, I'd not think the problem originates with the grout itself. I'd venture it has to do with something done post-installation; the cleaning, or the sealing. So many variables, but the overall blotchniness? Could be the application and use of the product used to clean the grout shmears off of the stone. If the texture of the grout was changed during the cleaning process, the sand papery grout can hold shower residue; soap and shampoo product, etc. Same with sealer use. If the sealer pooled in some areas versus others, or if the sealer dried on the surface, it can become tacky on a micro-level. You may not feel it, but it can hold dirt off the bottom of your feet, or hold shower residue. The following two things will typically whiten grout versus causing it to go darker: Could be efflorescence, but with the linear drain I'm guessing you have a surface applied membrane under the tile. Efflorescence is more common when tiling over an improperly built mud bed or a slab. Could be latex leaching. Latex leaching can be effected by water usage during the installation, as well as an insufficient grout drying/curing time before the shower was used. Latex leaching will typically lighten a surface, but the latex can hold dirt. No solid answers from me. Just speculation.

Im gonna insult you likely. yet its not my intent. These scenarios happen daily to the point of being an epidemic within our industry on account of unqualified labor. A red warning flag to A homeowner is A handyman willing to do PARTS of a tile install especially A shower build. In the professional tile world we dont engage in these scenarios for many reasons. The biggest being liability especially when we wrrty our work. This combined with Installing rocks on A foam pan tell me this guy is not qualified to work on your shower. Every tiler knows there is a high likelihood of failure when installing rocks on a foam base. You are experiencing point loads and there is no fix. Most true pro tilers avoid foam bases completely yet many novices swear by them.. Your best bet is to completely tear it out and this next 3X MORE expensive time around source and hire A qualified tiler. There are still a few tile pros here on houzz that would be happy to help any homeowner source a tiler in their area. Its just that nobody comes here to houzz asking for hiring help. Yet they always arrive angry with the disasters. Homeowners reading along You Always want to place the entire tile process SOLEY in the hands of the tile installer. This means allowing them to supply every material and installing everything from the studs OUT. including the subfloor. Adding to that A solid written contract with a detailed scope of tile standards to be met and followed. as an aside: " You don't remove it; you tile over it which is a TCNA approved method. No waterproofing risk. " tile over a disaaster !!!!!!! Stick to countertop advice buddy XOXO

Don’t put glass on the floor. It could break if something was dropped on it. I haven’t done a shower floor yet. Kohler made a cast iron enameled shower pan that was similar to a tub I had that was pretty safe. If I wanted pebbles, I might consider something like the flat marble mosaic where the tiles are shaped like pebbles, but flat. It’s not really pebbles and has a lot of grout. I think some pebbles would annoy some people’s feet. In a rental, I’d consider the kohler cast iron shower pan first. It seems safe and sturdy. Actually, the reason I have avoided shower floors for so long is that when I was renting, the shower floor leaked over and over again and no one could seem to fix it. I have used tub showers ever since. Hopefully there are enough solutions now that make shower floor leaks less likely.