I've been googling madly about silicone and this is what I've found. They are not all created equal and some of the cheap ones attract dirt. I think that's what's happened here. In defense of the fabricator, I think they haven't installed much white quartz and I don't think you'd notice the grimy looking silicone on granite. Also, I wonder whether they did an inadequate job of cleaning the surface before they applied the silicone. Maybe it looks dirty because there's some dirt in there? Do I have any recourse here? Should the fabricator help me out? It doesn't seem reasonable that 3 months out, the joint looks bad. I think at the very least, I should call the fabricator who installed my quartz and let them know that they need to use a higher quality silicone for white quartz installations. How do I find out which silicone is best when I replace the existing caulk? I'm worried about the silicone that's down in the joint that I won't be able to reach. I think they put a bead of silicone on the edge of the counter near the wall and then put the backsplash piece on top. That silicone will be impossible to get out. If I cover it with white silicone, will it look OK? Is white silicone opaque? I'm upset about this because one of the big issues I had with my old kitchen was that no matter how clean I kept it, it never looked clean (thanks to the 1970s color scheme). Now I have a new kitchen with a 15 foot long seam that looks grimy no matter what I do. Ugh.

That is, or should be, caulk, not grout. They probably used acrylic or siliconized acrylic caulk and that tends to shrink and discolor (white starts turning yellow). What you really want though is pure silicone caulk. And yes, the caulk can be redone. You don't want grout there... that's only good for flat surfaces on the same plane, you want caulk at the plane changes.

Help! I used a new cleaner for my quartz countertop and I think there’s bleach in it because it discolored a part of the countertop. How can I reverse it? What can I do to fix it?

I suggested the sanding/de-glossing as a solution because that happened to me on one side of my kitchen island. My quartzite is honed and on one side the edge we used (1/4 or 3/8") looked shiny very close to the edge. It was like a little 1/4" strip next to the roundover had been inadvertently polished to high sheen by whatever does the roundover. They came out, fixed it with some kind of compound that felt like the texture of whole grain flour (but made of stone), and it made a freaking MESS but it was all better when they left. They had a machine that looked like an angle grinder but with a wierd rubbery head on it. Joseph probably knows what it is. So ... that's the reason I suggest this. It didn't remove any material that I could perceive from the counter along that edge. It was just a surface treatment to even out the sheen.