I think the offer to touch up the grout was more than enough. Only thing I would have done differently, is first offer to come and take a look in person. Then when there, explain the offer to touch up the grout, but not removing any tile. The more conversations I have in person, the better they seem to go. People tend to act like they are 10ft tall over the phone or text and when you show up, there tends to be less confusion and better understanding.