If they had Canker, you would know by lesions and a foul odor.
If you are dealing with respiratory disease, then treat those that are symptomatic with an antibiotic like Tylan/Tylosin.
Looks like a scab, perhaps from rubbing on wire on from a feeder.
Could be a papilloma, hard to tell.
You can paint the scab with Iodine if you wish, but if it's not changing, then I'd be inclined to just monitor it.
Wet Fowl Pox - do you see lesions inside the beak(s) of your chicks...