It's not really 'sudden'. It appears they have been getting grain for quite a while. I think I have had them 2 weeks? I am not sure how long they've been getting it and none of my other birds are ill. They are in the coop, in a giant dog crate. I noticed a couple days ago they weren't as active but I thought they were hot (it's warmer now) and just reserving their energy. Looking back I could kick myself but we have been SO busy. We are putting up the fencing for the garden and tilling and spring cleaning and I have been really distracted. I am confident this is what it is. I feel awful for not seeing something wrong sooner.Seems odd to me that so many would all of a sudden have this. Perhaps there is something more going on? Any chance you can send the deceased for a necropsy and/or take one to a vet and have them look at the crop contents microscopically and due some fecal tests?
-Kathy