From what I have read, it could be gape worm. Wouldn't hurt to check it out. Symptoms do sound similar.
I have to admit that this is a new one for me and I had to look it up....but I'm not sure that they symptoms being displayed by Strudel, and now others in her flock, are indicative of parasitic infection. It seems more viral or bacterial to me....not that I'm an expert in any way.