A sour crop doesn't necessarily always smell. And vets don't always know what's best for chickens. This is why we have this place to come to for advice. Many of us have been caring for our chickens for a decade and more without the luxury of a vet to treat them when they turn up sick or injured. So we've learned quite a lot about what works and what doesn't, and we're still learning.
Sour crop can make a chicken very ill, and if it goes too long untreated, it can spread down into the lower digestive tract as well. Once this happens, the chicken is going to be slowly starving to death.
A doughy crop in the morning is a sign that the crop is in need of treatment. I urge you to go ahead and give the oil that
@Eggcessive suggested, and then begin treating with miconazole. You can get it at any pharmacy where the women's products are shelved.
Read this for further information on how to treat.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/ I also suggest you provide grit to this little patient if you haven't already.