Hi there, another uk chicken lover here. Have been battling a chronic sour crop/pendulous crop situation for the longest time, my Goldie's still going though!
The meds you need will depend on how bad it is. Is the crop full of sour liquid? If so, I've learned from experience that best thing to do is tip it out. If nervous pr If your chicken struggles this could backfire, so best not to do If lacking confidence. Oral Daktarin won't work if there's a ton of liquid in there. If it's not too full and smells yeasty and mild you could try epaom salts (1 tsp in cup of lukewarm water) over the course of the day. Any supermarket has it. Next step, oral daktarin. No need for prescription but need a boots or Yogi or similar pharmacy. Daktarin =1 ml syringe, 3x per day ideally. Could mix into soft food if she won't take it (scrambled egg works for me). Dont use the foot cream, need the oral version. This didn't work for my Goldie but she had a bad case, lotsof brown stinking liquid.
in the past Canestan vaginal suppositories have worked for me. There's a good article on dosages somewhere on here. If you want this route I'll look it up. You can get this easily on online chemists with a small questionnaire & express delivery. Again Boots will have it. You'll have to claim you have an infection down there to get it!
If a really bad case, get Battles pure copper sulphate and mix the correct dosage. If interested, can send you more on that. Can get in one day on
Amazon Prime. This works amazingly well for stubborn cases. However takes a toll on the bird, so best if she is not too thin and weak already.
What's causing the sour crop? Do you know? Must be something underlying it that needs fixing. Is it blocked? Any funky smels or other symptoms?
Good luck!