Small amounts of yellow spit up on 5 month old babies sleepsack. We had him at kids hospital last weekend due to the same, this is the first it's happend since. The doc said they weren't 100% sure what it was but could be gastric contents or bile and they weren't concerned. I'm worried as when he was born he was rushed to nicu due to bilious vomiting but they have said they're confident it's nothing to do with that. Has anyone else's little one had this yellowy spit up? He's exclusively formula fed. Pics attached for reference.