If you can catch him , I would to check him over, feel his breast bone, make sure he's nice and thick and not loosing weight or anything like that. They are pretty tough disease resistant birds in general, but they still can get sick at times. See if you can watch his poop too, make sure it's not off colored, super runny or just out of the ordinary.
If you do see any of this, I'd quarantine him if possible to be safe,
Hopefully, none of this will be the case, could very well just be all this high heat everyone is having, they are just like us, if it's super hot, they are less active, but any time one act out of the ordinary, it's best to check them out real close.
Let me know if you discover any thing unusual with him