Right. It's not uncommon for a hen to have Crop/Digestive issues/symptoms when dealing with a reproductive disorder. Once you get inflammation/infection under control, an egg or lash material is expelled, etc., then often the digestive problem starts to resolve as well. (Or vice versa)...
I would try what @azygous has recommended or if possible, reconsult your vet.
You mention you had 2 hens treated within the last 6 weeks - what for - Coccidiosis and Salpingitis? With what - Amprolium and an antibiotic?
I'd hazard a guess that the material you found is lash material, but...