Shower floor is 1 inch honed marble and walls are honed marble subway. Proper pan with an appropriate pre-slope and cement board walls all coated with multiple coats of liquid waterproofing membrane. Entire shower grouted and then sealed 7 days later by the homeowner. All changes of plane received siloconized caulking. After first use it was noted that certain tiles and grout lines were darker than others and stayed darker. An investigation revealed that on the vertical wall of the built in shower seat opposite the shower head (about 6 inches above the floor) there was a one inch gap in the grout line.
The supposition is that water makes it's way in there and then flows down in a sort of meandering line under the tiles and to the drain soaking the grout and tiles along the way from underneath. Careful inspection revealed no other gaps in grout or caulk lines. It is also possible that the homeowner missed some small areas with the sealer.
After 7 days of no usage with a high powered fan moving air across the tile there is little change. The missing grout is not yet repaired and the shower has not been resealed in the hopes that the moisture will work it's way up and out.
Is there anything further that can be done to speed the process? Perhaps a dehumidifier in the shower?