who tiled that? they were stingy w/the grout (or they wiped too much of it away w/the sponge) I don't think the grout has discolored, I think what you're seeing is the gray mortar that was used to set the tile. (and if you tell me he used white mortar, then I guess it's not the problem! sure looks like gray thinset though)

take an exacto knife and try to scrape it. is it hard like cement mortar?

can you get another close up of the discolored part?

what kind of grout was used?

not enough grout is between the tiles. you should not see obvious dips or be able to fit your nail in between the tiles.

needs to be regrouted

my other question is , "why did you wait 6 months before bringing it to the attention of the tiler? "

Beth H. - thanks and I think you're right. That's good if it is just slapping on a little more grout and fixing the cause of the problem.. Whew! Our master bath was the last step in a 3-1/2 month reno and I guess the hexagon tile was challenging to put in (lots of cutting), so the tile guy probably rushed the last part a bit. He also was probably not too happy we had him redo the niche since it looked funky the first time.

I contacted our contractor a couple months ago but had to be a shade persistent in getting a response. I didn't go into the back and forth with him in my initial comment because I wanted to be as succinct as possible.

Again, thanks and this aligns with a real fix instead of some slipshod bandaid.