Gold barb gill wounds?

Hi! I’m new here. My 1 year old gold barb have some wounds on his gills which looked like nothing else I've seen. It looked like flesh stripped out of his gills!Anyone know how to treat it? Many thanks!
also here is the info for my tank:
2 gold barbs
3 wild type gold barbs(Chinese/green barb)
3 male Taiwan bitterlings
5 Japanese medaka
4 small white cloud minnows
4 freshwater clams
4 limpet snails
unknown amount of cherry shrimps(they had shrimplets, I can’t count how many)
the injured gold barb is still eating food, and I have dosed a teaspoon of aquarium salt to the tank .

tank is 20 gallon with loads of coon tail plant and pothos

Looks like an infection, though I'm not sure what it is. Hope someone can ID the problem.

Oh man it just got worse! The wounded barb just got a new wound at his bottom. Would it be parasites? Please help! He’s still eating though, and the water parameters are ok.