I just went put a bowl of regular water and he got down to what looked like eating. I can watch closer next time. I don't have any heat on him now but I can put that also. The crust was gone form his mouth. Do you know if that Metronidazole comes in a liquid form that @Wyorp Rock recommended? And can I get that at a feed store or TSC?
Check inside the beak very well for any lesions/plaques. If the crust is gone, it could have been mucous or similar due to sour crop, since you mention that his breath has a smell.
You do not want to treat with Metrondizole unless you highly suspect or get confirmation that the cause of his symptoms/illness is Canker. If you do find out it's Canker, getting a script from the vet is best. Metrondizole can sometimes be found at fish/exotic pet stores or you can order it online. Same with Acidified Copper Sulfate, you most likely will not find it in stores, it will be ordered online.
Here's some good info on crop issues:
http://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
fwiw-Infectious Coryza reportedly does have a very rotten smell, but it is a respiratory illness - generally there would be obvious eye/facial swelling with a thick yellow foul discharge or pus, accompanied by mucous from the nostrils, sneezing, coughing, etc.