Efflorescence – A common problem in shower floors and surfaces, particularly in wet areas.
Due to soluble salts rising to the surface. When moisture reacts with naturally occurring salts in the grout, efflorescence grows. Yes, it GROWS. Salt crystals will grow, expand and will find a way out towards the surface. Sometimes this leaches out directly through the pores of stone, but more often it finds its way through the path of least resistance, the joints.
Fortunately, this can be resolved and prevented from happening again by calling Grout Guys, LLC at 919-740-0984 for a professional technician to treat it.