Unfortunately, there is no fan in the bathroom. And I don’t know what kind of caulk my contractor used.

Thank you Millworkman. I have to replace our silicone caulk too!

" Unfortunately, there is no fan in the bathroom "

Then, unfortunately you will never stop the mildew. Spend the money and add a good fan.

@millworkman - thanks. Someday, I will. I asked my contractor about that when he was doing some other work in my home, and, apparently, it would be a major expense - such that if I put a fan in, I might as well gut/remodel the entire bathroom, which I'm just not in a position to do right now. I understand that that means redoing the grout every couple of years.

You also need to remember, grout is not nor was ever intended to be waterproof. Water passes thru the grout so expect a moldy rotten mess behind that tile when you finally do the gut. Not trying to scare you but what you see is usually the least of the issue.

That is already past the point of needing replacement. It's guaranteed to be leaking, and have mold and rot issues. Caulk will not fix what is wrong here.

Thank you everyone. I have a call into my contractor.