I installed a backsplash this week and am thrilled with the results (my first tile job ) But as i'm cleaning the tile getting ready to grout i've noticed that some of the accent mosaic pieces are not adhering very well. So my question is: Do i leave them alone hoping that the grout will secure them? or do i look for a (small) container of different adhesive and resecure the loose ones before grouting? (I used mastic for the ceramic tile and the mosaics)
How long have they set? Perhaps it's not dry yet, or perhaps it got a bit dry before installing the tile, or perhaps it wasn't pressed fully into the mastic. In either case, no you cannot rely on the grout. Resecure them by taking out the piece of tile, scraping out the old mastic as best you can, and resetting with fresh mastic.