Structural Grout Do I Have To Replace Grout That's Falling Out Around The Tub? The Bathroom Floor?

Do I have to replace grout that's falling out around the tub? the bathroom floor? - structural grout

The house is old, but the bathroom is only 18 months (Reno). Mosaic tiles has never been right, but now I find the cracks and joints fall around the bathroom (ceramic), and even on the floor the same - Ceramics (). Everything was concrete under and behind him, but I'm worried about mold and water and structural damage possible. Suggestions? Is it absolutely necessary to remove and replace, or replicate even the tiles? The installation program does not use braces, even when asked about this question, it would be a bear to return to the sauce, I bet ...