The tiles do not need to be replaced. Do you have any scraps from the job?
Start with applying some vinegar to the extra piece of limestone. Let it sit for about 10 minutes, followed by drying off. Compare the severity of this etch with the one that is on your job. If similar, start with a 200 grit sandpaper and practice on your extra piece. You might be able to rub it out by hand or go right to your grinder.
It is imperative that you go as deep as the deepest part of the etch before you move up to the next grit. Follow with overlapping with 400 grit to take out the 200 grit scratches. If you use the sandpaper dry, it will automatically glaze to a higher grit. If you use it wet, it should stay fairly even. 400 may be your stopping point. Pressure, rpm's, feathering, and a watchful eye will determine how successful your blend will come out.
Use caution not to "dish" out the stone. Did I mention to practice first?