Random toddler vomiting

[SoozleQ]

My 17 month old vomited once on Friday night, was fine all night (including breast feeds during night), then puked in the morning after some cow's milk (so 12 hours later). We kept her off milk and she seemed fine - eating fish fingers and beans for tea and keeping all that down. We went to feed her breakfast and weetabix with milk came straight back up (24 hours after last puke) so we though milk might be the culprit. Kept her off milk again, she didn't want much to eat for lunch but seemed fine playing in the park but then randomly puked this afternoon (6 hours or so after last puke). She hadn't just eaten or drunk anything and brought up the banana she'd had 3 or 4 hours earlier. Other than puking, she seems fine. No temp, not unduly lethargic, just a bit more cuddly but still with energy and she's keeping down water.

Is this just a bug that we're all going to come down with? It's the time between pukes that seems strange to me. Any ideas?