Reoccurring sour crop

She is an older chicken, at least 4-5years old. Back in the summer she developed water belly. We treated, drained the fluid and she recovered very well from it! But now she’s constantly having issues with sour crop. They’re fed master feeds laying hen pellets, they get scratch grain daily, as well as meal worms and other treats (fruits & veg). It was recommended is use clotrimazole to treat. She improves while she’s being treated, but as soon as I think she’s in the clear and stop treating it comes right back. Her crop fills up so much the fluid comes back up, and it always has small feathers in it? But not her own! Smells absolutely horrible, yellowish/brown What do I do? Is this even sour crop or am I dealing with something else? It’s been weeks of treating her Editing to add: they get chicken grit and we also put ACV in the water