Kathy Golla
Crowing
Over the decade plus that I've been keeping chickens, I've had more than my share, ashamed to have to admit, die from pesticides and petroleum distillates. I could write a book on how to be stupid while keeping chickens. The symptoms you describe fit pretty well with toxic poisoning that I've experienced first hand.
Bacterial infections from viruses shouldn't be so sudden and without any warning. This goes for parasites such as coccidiosis, as well. You will usually see a sick chicken slow down, act "off", then gradually develop more concrete symptoms. Toxic poisoning strikes immediatel and death occurs very quickly. Insecticide will produce a saliva discharge from the beak, often yellow.
When I lost a month old chick suddenly like this, I suspected poisoning, yet it took me two full days of covering the same ground over and over and over to suddenly realize the killer was sitting right in the middle of the chicken range area in full view.
It was my log splitter. It leaks hydraulic fluid onto the soil. Chickens eat the dirt for grit and are poisoned. I've also had a rooster knock over a can of wasp spray sitting right by the run and spray a hen right in the eyes, and she died, exuding yellow stuff from her beak.
I've had chickens drink from puddles from planters after they had been watered and been killed by the insecticide leaching from the soil inside the pot. There are also poisonous mushrooms following a rain, and the red ones that chickens would notice are especially poisonous. Lead paint flaking off an old shed can cause serious problems, and soil where paint brushes have been rinsed in thinner is lethal.
If you suspect poisoning, give an activated charcoal tablet, followed by a molasses flush. But you need to locate the source if this is indeed why your chickens have been dying.
All, @azygous just posted this on a thread. I thought this is super informative and very true. I wanted to share it out.