lucrbc- Thanks! That does make me feel lots better. Bella definitely can too, I guess she's been my one and only baby girl for so long I fret way too much.
Britster- Your Jackson is just ADORABLE! I think his weight is the perfect size
OwnedbyJezebel- Rocco had one of those immense growth spurts too, but not in one week

That's really amazing! Is she still 19 or so weeks? At what age can I expect Rocco to start slowing down? I was thinking 6 months to a year.
Gennies- I love the name of your little one

Forgive me for my ignorance, but what is colitis?
DerbyLane- You're right, it's definitely the puppy teeth! He gets way too excited in the middle of their play, and bites down too hard. He stops right after though, and leaves Bella alone for a minute, so that's good. I heard that Yorkies lose their teeth; when should I expect his to come out? They're all so pointy, and tiny, is that normal?
Thanks everyone for your replies! I'm sure he and Bella will be fine, the trouble is just convincing my husband that 12 lbs or so is not bad. (He worries about Bella, too--she's such a Daddy's girl

)