Hold on please.
I had the same issue with my birds but it was because I was picking them up incorrectly and putting pressure on some sort of their esophagus/chest/gullet/whatever immediately after they drank. Putting pressure on that area causes them to "vomit" and it to inflame (and continue like you saw). It wasn't really a vomit in the sense like humans, more like "un-swallowed" liquids that were forced back up. Sorry to be so vague but I'm too tired to look it up right now.
I'm not saying to not pay attention to your flock and dismiss any concerns, but I wouldn't get crazy yet. Ascites, heavy liver damage, cancer, etc., should have other symptoms associated with them and would (usually, not always) be noticeable. No need for culling just yet unless they are definitely going down hill.
Had one of my one month olds do it today while moving them from the shop to the coop, actually reminded me of why I looked it up in the first place.
Hopefully someone else with more experience will chime in, but that's what I've encountered.
yes, I'm pretty sure that i picked them up to fast or to hard because it hasn't happened in about a week. thank you all!