I was responding to your statement that you suspected gapeworms. The link I provided you is from an expert who has dealt with them. Thankfully I've never dealt with gapeworms. Knowing my soil would be contaminated with their eggs, and knowing there would be endless worming treatments trying to...
Please read posts #13 and #14 regarding treatment for gapeworm in this thread:
https://www.backyardchickens.com/t/602699/worming-chickens/10#post_7931599