I have a six+ week old Rock who has sour breath for a couple weeks. In every way (eating, drinking, poo, energy etc.) she was fine but definitely had sour breath. I began giving them all extra yogurt. Olive oil was suggested to me as well but I did not really like the ideas for getting her to eat it, like using a dropper and dripping it into her beak on the right side to avoid her aspirating it. Too risky for my taste. Anyway, they LOVE their plain yogurt so I added a couple teaspoons to about 1/2 cup of yogurt and they gobbled it up AND the sourness in her breath is gone. I can only credit this remedy and adding the olive oil to the yogurt made it super easy and they all benefited. I realize this wouldn't work if it is to the point a girl isn't eating but if it is caught early this really seems to have worked!