If it's me, I would treat them with Api stress coat, plus, handful of epsom salt... Water change twice a day 30-35%, good amount of oxygen.
Does it look like a bite from another fish, if it is, It should be back within days, if it's infection, need extra care.
Api stress coat has aloe vera gel and kind of water softener, used to treat a fungus, with handful of epsom salt to kill bad guys. (many don't agree with me on salt things and Api stress coat but I did it successfully so It's my experience I am sharing)