He passed away roughly 15 minutes ago. He was with the whole flock which has 5 cockerels, him included, that we know of for sure. Two of those are mad smaller than him. I didn't see any injuries on him what so ever.
As for getting into something, there is a chance. We have nightshade species that grow all over our 13 acres as well as a few other toxic plants (pokeweed, etc). Rotten or moldy things, most likely not unless one of our cats left a kill in the tall grass which is possible.
He was opening his eyes towards the end when he was trying to move. We tried both sugar water and Sav-a-chick water but neither helped at all.