I have a sable American cocker, but I am sure the same applies to the English. Sable is one of those colours that can change quite dramatically in the dog's life time. My Jesse started out very dark and now at 6 years old, he is quite light. So yes, I would say that what you are seeing re colour is normal, however, I am a bit worried about shedding. A 10-week old puppy doesn't normally shed yet...
