Hi, I'm no expert on puppies but when they're born they weigh around 2-4 est ounces. They fit in the palm of your hand and have a tiny head. By the time they get to 12 wks they've grown alot. They are around 2-3 lbs and their head is alot bigger. The hair on their head and on their bodies is changing also. They are starting to change color, getting rid of their puppy coat and grow new hair. The hair on the top of their head is getting lighter and for a few weeks it makes them look pretty bald under the black. It is thinner because their head has grown and the new hair is just starting to fill in. Give it a few weeks, you'll see a big difference. Good Luck.
