A couple of Erin's have come by themselves, but the rest came in pairs - I don't know whether it is common or not though! But, I would personally think that the grizzles could be teething, as IMO it is a continuous process until everything is over. She cut #8 about a week ago, and I think #9 is moving up and down a fair bit, as I swore I could see it a couple days back but checked today and was barely a bump