That's possible. He also could have a bad heart from his weight and gets dizzy when first trying to stand. Sounds like he's a broad breasted variety, they aren't destined for long lives. How much do you guess he weighs out of curiosity?
He could have botulism from eating moldy feed, but usually they become paralysed, especially in the neck. He also could have sustained a head injury. This time of year my first thought would be encephalitis caused by mosquitos. Not much you can do for any of them unfortunately.