No obvious bad odor from his beak. Judging by my book its not always present in canker but might be. Conditions with similar symptoms are listed as being sour crop or wet pox. I don't think it is sour crop.
His symptoms match canker more closely than pox, but I don't know how to tell definitively
Are they likely to spread canker it if they don't have an active infection?
I still don't understand how he got it. They are in an enclosed coop and run. No wild birds have direct access to their food or water. I use nipple waterers, so there isn't much opportunity for crud to fall in the water.
None of the rest of my flock seem ill.
I have read that treating the water with acidified copper sulfate once per month helps prevent infection, but I don't see how that is protective for the days the water is not treated.
I am struggling with whether to cull. I don't want to infect my whole flock. I can't house him separately forever. I don't really consider them pets per se, but I am fond of my flocks.