Separate the fish and check progress daily...if you don't see even a slight change after 2 full days of antibiotics, then you have another problem. Parasite is my guess. Does not look fungal, but bloody fins from the edge in can be an indicator...you're going to have to get on it and watch. No matter what, don't stop the antibiotic treatment until the prescribed period is over...depends what you use. Also keep an eye on the other fish...this one might just have been immune compromised from something and is showing first signs.