Chicken not being able to eat, now growth on beak

[Wyorp Rock]

I was thinking possibly canker.

If in fact it's canker, it will spread to your other birds via waterers/feeders. Birds remain carriers for life.
Treatment is acidified copper sulfate. Dosage is 1/4 teaspoon per gallon of water for 3 days straight once a month. Use a plastic waterer to provide it for your birds.

Your answers are from @dawg53 on page 1

If you can't find Acidified Copper Sulfate then see if you can find
Metronidazole 250mg once a day for 7 days.

 

[Chicalina]

Your answers are from @dawg53 on page 1

If you can't find Acidified Copper Sulfate then see if you can find
Metronidazole 250mg once a day for 7 days.

I've just found this on canker and it looks like it might be helpful. Perhaps alongside the abx you could try the treatments suggested in this article http://www.poultrydvm.com/condition/canker

The article I linked to gave treatment options too.