I have this happen to me quite often. It's from not cleaning the grout residue off the tile good enough. When there's some grout haze left on the tile the grind from the back of the tray shows in certain light, I haven't seen the word Avaire on the tile yet.
If you used the acrylic grout then have the installers use acetone to clean the grout haze, if urethane grout use Krud Kutter. Both are available at most home centers.
Let me know how it goes.