Concrete unilock pavers - Black spots

[Windsor2013]

I recently had Unilock pavers installed (Europavers) 1 week ago. I am seeing a bleeding of what looks like black ink on top of a few pavers. It wipes off (some of the stones have a small pinhole under the ink) The Unilock rep said "birds eye" possible vein in the rock used from the query. Has anyone experienced this? familiar with this? will it continue to happen? No one has ever seen this (Unilock is the largest paver co. in the world)