Tooth Color Change After Veneer Replaced, could the clear glue have traveled?

Porcelain veneers were applied to teeth 5-12 in 2006 . Recently the veneer on #6 came off and was reattached using clear glue (white glue was originally used). After that my natural dark color began showing through the veneer. Now the color of 3 other teeth with veneers is darker. Could the clear glue have "traveled" to them so that now my natural tooth color is showing beneath them too? The dentist says it's a "coincidence" that now the other 3 teeth appear darker. Coincidence???