Rough debris on the 8000 stone? You mean black shmootz (swarf) or some sort of foreign material? If you felt any sort of hard bump it may well have rolled or chipped the edge, and it doesn't take much of a hard inclusion to do some damage.

You did lap the stones correct? Remember to wash the stone too, before honing on it. I always hit them with running water and brush the surface clean with my fingers to be sure it's free of foreign material.