Oh yeah thats infection of his barbels, not good either.
They need sand, for this reason, its too easy to damage their mouths on rough gravel trying to dig out the food and gravel is easy to trap waste unlike sand so with bottom dwellers like cories it usually ends up this way.
I would also check your ammonia,nitrites, nitrates, and your GH.
Do daily water changes to keep it as clean as possible and change out your gravel for sand asap.