There's no mention of when she last laid an egg, is she laying at all? Have her eggs been normal hard shelled eggs?
How are you treating the Sour Crop. I use a yeast/anti-fungal medication like Miconazole or Clotrimazole to treat Sour Crop.
Usually a crop issue is a
Symptom of an underlying condition, a few common ones are Reproductive disorders, Infection, Worms and/or Coccidiosis.
With her being a production bird, she may be having some reproductive problems. It's always hard to know. If she's not laying eggs or has had problems with production, then the likelihood of this being reproduction is greater. Cancer, EYP, Salpingitis, etc. are common in laying hens.
Give the Correct dosing of dewormer (Fenbendazole) as state in
Post#8. Finish the Corid since you started it. I'd also begin addressing the crop symptoms, information about what to use and how much along with treatment is in the article below.
Do continue to encourage her to eat her normal feed. Hopefully she can make a turn around and improve for a period of time.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/