Pullet with foul smelling beak and black under tongue

[chuckachucka]

I have a 6 month old Japanese bantam pullet who has recently been a bit smelly. Her poop and behaviours are all normal. But i realised today the bad smell is coming from her mouth. So i checked in her beak and found that under her tongue there is like a layer of dark grey matter that goes down into her throat, attached to the underside of the tongue.
It smells very very bad.
As far as i can tell there is no issue with her crop and she is eating and pooping normally.
What could this be??

 

[Eggcessive]

Do you see any yellow material as well? Do you see if the tongue is normal and if there could be something stuck in there? Can you get a picture? A bad odor from the beak can sometimes be canker, a yellowish cheesy infection that affects the mouth, esophagus, and crop. It is treated with meteonidazole (Fish Zole) and a few others. Another cause for a bad odor is coryza a respiratory disease.

 

[Eggcessive]

Some pictures of suspected canker: