If it's the poop in the foreground, that's a very healthy poop. It doesn't indicate yeast as yet. You've likely caught this crop issue early enough where yeast won't be a problem.
You can use any vegetable oil. Just be very careful you don't get it into the airway. You can syringe it into the...
This should get you started. https://www.backyardchickens.com/articles/how-to-treat-sour-crop-and-impacted-crop-and-how-to-know-which-one-youre-dealing-with.73607/
I'll be around to answer questions.