Cracked tile in bathroom

The travertine tile in our bathroom which is part of a 5 year old addition has started to crack and come loose in some places. What's the best strategy for repairing it?

The Money Pit Answer

Are these floor tiles?  Typically tile that cracks has an uneven surface below it. First, make sure you can find replacement tile that matches.  Then,  I'd remove the cracked ones and clean the base very carefully.  Next using tile adhesive, I'd be sure to fill in any low spots so that the tile can't flex once it is reinstalled.  As you've learned, tile doesn't bend well!