Thank you for the update.Butchie update. Trying something new. So I had to go into town several days ago and my husband threw some leftovers to the chickens -- nothing too heavy, just some roasted beets and carrots. The other chickens were fine (just some purplish poo from the beets), but Butchie had a short crop episode. Her crop was big and full the next morning. It hadn't even gone sour yet. There was no smell -- it was just backed up. She was on day 3 of acidified copper sulfate for the bloating I was noticing in her abdomen, so maybe that helped the crop from not going sour.
I did the usual treatment that's worked on her before: no food for about 20 hours, just water and a tsp of oil, lots of massage. The crop cleared after one day. I gave her an Epsom flush, then after a couple hours fed her egg and sweet potato and the crop cleared fine by the next morning. She was tired and wanted to sleep most of the day yesterday, but today she is much better, and very hungry.
From this crop episode and the last one about five weeks ago, I'm really thinking there's nothing wrong with her crop. She has some cyst or inflammation making her abdomen swell and constricting her lower digestive system. Whatever is wrong with her, it's not her crop, that's just the final symptom.
When I noticed her abdomen beginning to swell and harden again, I also noticed that her vent had gone from a little circle to a coin slot shape. She sits for about an hour each day "nesting" and her butt pumps, just as if she were going to put an egg. So she's "in lay" even though she does not produce eggs. Lucio the rooster also noticed and stalks her. He caught her and mounted her the day her crop was full and poor Butchie almost suffocated. I keep her away from him now. But it seems like the combination of her oviduct trying to work is inflaming and putting more pressure on her other organs.
So I stopped the copper sulfate, waited three days for her system to clear, and started her on a course of Bactrim (sulfametoxazol) as @Two Crows suggested a few weeks ago. And I'm giving her a tea steeped with oregano, turmeric, and ginger to drink (she seems to like it) for the inflammation. Giving her the antibiotic seemed illogical to me given the sour crop that surfaced a few times, but given what I've observed recently, it seems worth a shot. She could very well have some chronic cystic condition with E coli or other bacteria that is worse when she's "in lay."
She's on day two of Bactrim -- I'm using an oral suspension for children, 50mg once per day. It's making her poop like crazy, very watery, but I'm keeping her as hydrated as possible. The hardness and bloating in her abdomen has already subsided a lot. She's acting normal again. Cleo keeps her company. So that's where we are today. View attachment 3499263
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Of course I love to see Cleo included with Butchie in photos

Often the crop being slow is a symptom, so you would be correct in thinking that very likely something else is going on. Something reproductive is what I've found in my hens that had a history of slow/doughy/sour crop.
So, getting the inflammation under control may help alleviate the current symptoms you see until the next go round. These things tend to be chronic once started.