Well, I'll throw out another wild one. I'm looking at those joints and they look wider than 1/8". And you said he used unsanded grout? And it appears this guy like to water his grout...I'm almost thinking that if he did a lousy job the first time around, he had problems with the unsanded shrinking during the curing. Especially if he likes water. Maybe a little flaking, a little cracking, a few pinholes opening up. Then he came back on the subsequent visit and grouted again over the existing grout to hide and fill in the blemishes. But that's just too crazy for me to speculate like that. I'm almost tempted to recommend a few ideas, mainly try a Q-tip dipped in bleach to see if the dark stuff low on the wall isn't mildew, and try a bit of an acid, even mild vinegar, on the white stuff down low on the wall to see if the white stuff is efflorescence that the acid will dissolve away. I keep coming back to your first photo: In the vertical wall-wall corner joint that is grouted, the right part of the grout joint looks like the original quartz color. the white stripe on the left part of the grout joint, as well as the white in the horizontal grout lines above the first course of tile, looks like efflorescence. The dark along the tub looks like mildew or moisture. But if the light and dark have been there forever, both efflorescence and mildew take a while to form. If your water has heavy minerals or it's heavily chlorinated, that might be a player. If is he used old bags of grout that were past their shelf life that could be an issue too. Or a contaminated mixing bucket. Or... But as you can tell, I'm just scratching my head and guessing. Does the white grout have a different texture? If you scrape the white with a fingernail, does it powder off? If it does come off, is there any of the true "quartz color" underneath it? Have you tried cleaning this grout at all? Like in my first post, I just keep leaning towards the idea that too much water was used. When I first looked at the photos of the upper walls, they looked like areas of good grout with a few blotchy dark streaks. Now I look at them and see the uniform light color being almost all efflorescence, or I'm seeing grout that has had the surface cream/pigment washed away, and the "dark blotchy areas" are actually the proper quartz color! I'd love to see this shower with my own eyes to figure it out. I probably have to take my son down to William and Mary for a college visit later this month. Bill, how about a road trip? A few crab cakes, catch a lacrosse game while we're down there, we can check out this shower all while taking my son for a college visit? Too bad the Orioles are going to be at Fenway instead of the other way around. Road trip!!! Seriously though, have you tried cleaning the grout with anything? A neutral pH cleaner and a bit of elbow...

I've posted so many times lately about This Old Grout that I'm sure people think I'm a plant from the manufacturer! just as I have about Aquamix. :-) Fly-- it's not "like" an epoxy. It IS a one part epoxy, and I've got customers who've had their colorant down for alot more than 5 years. One other benefit of the colorant is that it permanently seals the grout and puts a finish on it that's just as easy as the face of the tile to keep clean. As for the "this old grout"-- I've never used it, but I've heard alot of good things about it.

We just used some kind of grout paint/recolorant (Lowes and Home Depot both sell it) to darken the floor grout in our hall bath. It was stained beyond cleanability so I figured I didn't have anything to lose by trying the paint. It actually worked very well and you'd never know it wasn't actual colored grout. We haven't had it down for too long but so far, it seems to hold up very well (I have had to scrub a few spots and none of the paint came off.) The paints seem to be colormatched to the grout lines sold by the store so you could probably get the grout paint that matches whatever color you are going to do on the wall grout. It is a little tedious to paint it on but it wasn't that hard - I was done in a couple hours. If your tile is smooth and your grout lines are straight, it will probably be even easier (we had kind of rouge-edged tiles that made the grout lines kind of wavy which was more tedious to paint.) So you could do the wall grout dark and then if you didn't like the way the light and dark looked together,you could darken the floor grout to match -- that is what I would do. I have white square running bond tiles with darker grout (delorean gray) in our master bath and I love the combo (not to mention the dark grout is so much easier to keep clean).

Your pics have now appeared they were not there prior. Rather than edit my previous post I will mention that your shower backer is an approved shower tile backer board. However I have my doubts about the proper screws and definitely think the pattern if incorrect. Also this board is NOT waterproof and there needs to be waterproofing done. Can be either poly sheeting behind the backer or a topical surface applied waterproofing. Also the joints of the tile backer require taping with a non-alkaline tape and taped with thinset. I see none of this but we do not know if any of this was done as we do not see the tile being applied to the wall.