What you are seeing is not fungus, it's the result of aggression. Scrapes & tears will show some whiteness, some colors show this more readily than others. Rid Ick will not eliminate this, reducing or eliminating aggression will. If the discus are being aggressive towards each other, they are probably giving the angel some grief.
Pairing and breeding fish are often slightly torn up, they are different from show fish. Keeping up on water quality will prevent any infection from setting in.
Black angels are the worst I've seen for showing any marking. A little chase & sideswipe some driftwood, and they show horrible looking white scrapes. This heals in a day or two with good water quality. Medications do nothing for this, as it is a situation that doesn't require medication. By medicating in a situation that doesn't require meds you risk creating resistant strains. If you need those meds to work in the future, they won't work as well, if at all.