As for the hippo, it looks fine. Just keep an eye on the area to see if anything actually develops.
As for the YT......is he in a display or do you have the fish in a QT for treatment? Any way that you can separate him so that we can work on saving him??
As for the doctors, you're doing a fine job with taking care of your fish by using QT. When you finish the hypo though, for good measure, you should keep the fish in QT for about 5 more days before return him to the display....however, if you're going to be getting a shipment soon, then, of course, you don't want to put in new fish with the fish you just treated.