I would think that the tan patches on the back of the neck would be a fault according to the AKC Standard. I have included a link.
American Kennel Club - Rottweiler
As for the 15 week old pup, my Xasha had small patches of tan on the tops of her ears as well. I brought this concern up to the breeder the day we picked her up. She assured me they would darken to black. She is 8 months now and they are gone.