LImestone - Mildew issue

From reading your aricles, I may be out of luck but we had Durango honed limestone installed in our bathroom shower floors, walls, bench and ceiling 2.5 yrs ago and have continual mildew problems - on the tile itself and along the grout (which a contractor has covered over with caulking along the base as the grout cracked). We live on the water in a humid area and already keep the fan/ AC on, clean weekly, and even leave the lights on to try reduce mildew growth. I have read that vinegar, bleach, grout cleaners,and scrubbers should not be used - any advice on what we can do for the mildew problem without damaging the limestone? Also, we have used bleach in the past and now have large spots that are no longer smooth/ shiny - do we need to reseal? Any advice would be greatly appreciated...we wish we would have come accross you website years ago.