Shower grout stays wet ?

Help please. I can't find a leak anywhere. After a couple of days of no use the grout in only one area of the shower floor and up the pan tile is wet. The water supply wall is shared with a closet so I took out drywall to confirm no leaking at the pipes from shower head to slab. The bladder is installed about 8-10" up the wall. Is it possible that after 2 years of NOT reseeling the grout, that water is pooled up under this area? Like I said I find NO leaks anywhere. Just 3 or 4 grout areas staying wet. Some are virtical. My only guess is that not good sealant on grout leaked or when drain was clogged for a short time water backed up under the bladder around the drain under the tile..???

Thoughts?? At this point I'm drying it out, making sure the drain is clear and reseeling the grout when dry.