Help Sick Peppered Cory

[captainpants]

My peppered cory has a red mouth, it's acting normal and i have only just noticed the redness today,
I think it might be septicimia but i just wanted to post and see what you guys think

 

[Pleccy]

Hi,

It looks like damage, which appears to have become inflamed. What substrate have you got in your tank?