There are lots of bugs going round, my 2.5 yr old has just had a horrendous sick bug. My 11 month old had a couple of weeks of projectile vomiting not long ago, always after her 7pm feed. It wasn't every night, but seemed to be the nights she'd had dairy at tea time. If she'd had egg (with milk and butter), cheese, or yogurt at around 5, then had a whole bottle of formula just before bed, it would often come back up. So I've laid off too much dairy at tea and it seems to have calmed down a bit? Am sure it will sort itself soon.