I would have gone with straight ACV - if it is Sour Crop, it is a fungal overgrowth and this can be knocked down really well with a pH shift. Of course, the copper would kill it, but it is a much more risky treatment, IMO. I'm not a vet, but I am a chemist. I don't think I would ever give my chicken copper sulfate, too much risk of toxicity for my taste.
I'm sure it worked, copper sulfate is used in common garden fungicides, so it would probably be great at knocking out a fungal infection in a chicken's crop. If it's not fully gone, I would recommend using the ACV as a follow up instead of any more copper sulfate.
I'm sure it worked, copper sulfate is used in common garden fungicides, so it would probably be great at knocking out a fungal infection in a chicken's crop. If it's not fully gone, I would recommend using the ACV as a follow up instead of any more copper sulfate.