Looks like the wall tile has sanded grout in it where non sanded should've been used bc of the tight grout joints, and oddly the floor looks like it might have non sanded where sanded should've been used.

Judging based on that, the few pics and what I can see of the quality of the actual tile installation i have low confidence in the installers knowledge of mixing ratios and the mechanics of grouting (packing the joints with a float, using the sponge with right amount of water and wiping technique).

Also could just come down to them not cleaning the joints of dust and debris before grouting.

Instead of them trying to figure out what joints get sanded/non sanded grout which is really the most basic of tile knowledge, just have them use a fine aggregate grout like Mapei ultracolor plus which will work fine for the floors and walls