It’s wonderful that Stretch has improved! I have a girl who’s been sick for about 4 weeks now. Vet did a ton of diagnostics and found nothing. Sunny is still eating very little and losing weight. No other symptoms like the mobility issues Stretch has/had—but I did see the same crop weirdness. Her crop isn’t sour or impacted—or even very large—but it hasn’t fully emptied in weeks. My vet says she suspects Marek’s, even though my chicks were vaccinated and I haven’t added any new birds.
Thanks to those who’ve responded here. I posted about my bird a few minutes ago, before finding this post, and the responses here have been helpful to me, too.