Naomi's missing her two front teeth

The first one she lost a couple of weeks ago, and the last one on wednesday. I don't know why, but it makes me laugh. :) The bottom two haven't fully grown in so the gap is exaggerated :) Does anyone know why teeth fall out at such random times? Her cousin that was born on the same day has already lost and grown all his teeth and Naomi has only lost 4. Go figure.