Fin Rot

[Shellyfish]

A friend of mine purchased a flame angel about a week ago. He said the fins were fine at the time. Now the tail fin looks a bit eaten as does the left pectoral fin, he is also not really using this fin, I'm not sure if it is fin rot or not, there is no white edge or cottony look, or maybe it it possibly shipping damage? He is putting it in a hospital tank, should he be using an antibiotic? If so, which one?

Thanks!