Hi - I am believing that mine all died due to the gnats. That seems so crazy, since I was feeling horrible that I had fed them something or they had poisoned themselves (which, still could be part of the problem, but this is beginning to seem more likely). But the only one that i saw symptoms for was kind of lethargic and wouldn't get up or move away from me.....just kind of sat down and just fell asleep. I looked at the 3 I have left, they do have bites/blood marks around their heads, take a peek at some of the ones that have lived to see if
they might be affected by the gnats. I also just let my 3 out to see what they would do, they acted completely terrified and trying to get under anything they could......now that I think about it, when I had them in the tractor in the yard, they wouldn't come down from the second level........also noticed there was some light blood in the crevices of their feet from pecking bugs away, along with head shaking to get the gnats off. If you are able, my only suggestion is to get them inside as soon as possible, I do think this could save them!
Sorry for your loss and understand your kids' sadness....my little ones have been wanting to have blue and green eggs for such a long time and now the girls are all gone.
Please post back if you find any indicators on your birds, would love to hear if it is similar to what I am seeing or if you find other things.....