Black cory with white mark

[Shushan]

Hi all

I have a black cory and I have just noticed a white mark on his face near his nostril. I'm thinking it may be fungal, anyone any ideas?

 

[Colin_T]

It looks like excess mucous. The other fish has damaged fins from something biting it.

Test the water quality for ammonia, nitrite, nitrate and pH.

Do a 75% water change and gravel clean the substrate every day for a week and see how it looks after that.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.