I feel confused, like I missed a whole page of posts...
You have hens and roosters as well as chicks. The roos were out free ranging when you fed them peas and watermelon. 2 hours later they were dead, now you have more that are dying? Symptoms include head shaking?
Is this right?
Okay, so we need a bit more information: How many birds are now ill? What are all the symptoms? (lethargy, not eating/drinking, poop look ok, drainage from eyes or nose). What do you use at the bottom of the coop? Any flowers or plants in the run that could be a problem? What does your feed/waterer look like? Has the food gotten wet lately and clumped (ergot grows in wet food as it molds and some feed containers have "hard to reach" places that it can fester in), also check your bag of feed it might have gone "bad"
Death in chickens like this is hard to determine because there are so many factors: impaction, poison, illness.
If more hens die then it is likely spreading and not necessarily pea related.
My advice would be to stop feeding all treats for the time being, quarantine the ones who look sick, bring them inside where you can monitor them. Clean out the feeders and waterers with a gallon of hot water and 2 tbsp of bleach (non-chlorine) let them air dry and then refill. Smell your feed before refilling, I have heard stories of mistakes by the store with the feed that caused death in flocks. I might err on the side of caution and buy a new bag anyway just to be safe.
Then keep a close watch on the survivors and let us know if any additional symptoms present.
Finally; if you have an agriculture office in your area, sometimes you can get an autopsy done to determine the COD, this would help if they continue to get sick. Knowing what it is will help you determine how to proceed with survivors or even if you have to start disinfecting the coop.
Hope something here helps!
