Has his comb been tinged white on the tips for a few days before this? In my experience, once the purple sets in it’s more severe. Be sure he has as much water available as possible and certainly never without. Had to save one with (tiny and modified) chest compressions once and he didn’t look...
Scrolling through trying to diagnose another issue for one of my hens and saw this. My apologies if I make any newbie mistakes.
I can’t help but notice the lack of feathers around his neck. If he has on a collar (crow collar, rooster collar, etc), it needs to be loosened - or taken off...
