ᐅ Grout in the bathroom: grout material on the cleaning cloth and residue on grout lines

Hello,
I have two questions regarding grout in the bathroom. We built our house three years ago, so the bathroom is relatively new.
Over time, we have noticed two things:

1. In the attached pictures, you can see some deposits on the grout. This is in one spot in the shower area, specifically on the last two rows of tiles below the ceiling. We hadn’t noticed this before. I have no idea what this could be or if it’s normal. Could someone please tell me what it might be?

2. While cleaning, we have noticed for some time that the cleaning cloth turns slightly whitish/gray. It seems like we are wearing away the grout when cleaning. We thought this would improve over time, but it has been happening for so long that we are starting to doubt that. We use water and bathroom cleaner for cleaning. Is this normal, or should we be concerned that the grout material might be too easily washable?

Thank you
Sven1903

Remote diagnosis is always challenging, but it does indeed look like the joint mortar is dissolving. After 3 years, there should no longer be a white haze. Basically, the joints need to be repaired! If the warranty period has expired, scrape out the joints (or use a small angle grinder) and reapply new joint mortar. There are also repair kits available at hardware stores.