InterestingChickens
Crowing
It may be a grain based feed. Could you please take a picture of the bag? Do your chickens have access to grit? Chickens need to to grind up whole grains. If it is indeed crop impaction this would be the cause. Give your chickens grit as soon as possible.Apparently, the food came from the breeder where we got them and wasn't supposed to be used as treats (at least that's what my mother told me) but I've had a look at the packaging and there is indeed some corn in it.
However, because two chickens have it and it was a relatively hot day where you are located yesterday it may be heat exhaustion as I suggested previously. Make it the only source of water. This is a link for how to make your own electrolytes for chickens: https://www.communitychickens.com/homemade-electrolytes-for-chickens/