Hi, ClodaghK,
Some of these tiles come from factories with a waxy film, which is supposed to be 'burned off' with the grout. Sometimes it is almost impossible to remove. There may be some residue of this still on the tiles. Check with the supplier and your tiler.
I find that I rarely have to use water, unless the floor is greasy. Because I have U/FH, the floor is always dry, and most stains come off with the floorbrush. I just have to wipe them as opposed to washing them.
If you have ivory grout, avoid using strong detergents on your floor, as the chemicals will cause the grout to deteriorate slightly, which will allow it to absorb stains.
Don't be on your knees drying that floor - use an old towel, and the back of the head of the floorbrush.