I have read a lot of posts on here where someone complains that their chick smells like sour milk, grain, or something else. We have a brood of 4 and one smells awful, enough to make you gag. They are 3 weeks old and she has smelled for a couple of weeks, but otherwise behaves normally. I just got some Braggs apple cider vinegar yesterday and am putting some in their water. But I cannot find anything online about 3 week old chicks with sour crop. There doesn't seem to be any definitive answers here about what the cause is, or a cure. I also started giving them grit, even though they are on purina medicated feed and supposedly don't need it. It's possible they all ingested some small pieces of wood chips before we switched their bedding. Their crops all feel the same. Otherwise I am at a loss as to this seemingly somewhat common problem. None of the local chicken experts I know have experienced this either. Could someone who maybe had this issue in the past help me?