Hi Steve and welcome to Simply. Is the gill problem sometime you noticed over time or did the fish come with the gill issue? I think I see the fish of concern in the video. The edge of gill cover itself appears to be turned outward with the gill material protruding from the gill. I suspect this resulted from either a defect or an injury. I do not have anything specifically to recommend but I do notice that the fish are breathing very hard. Juvie's do breath faster then adult but this seems really fast. Is it possible to add an airstone to the tank?
I am also guessing you are new to discus? I say this due to you trying to raise juvie discus in a planted tank with a deep substrate. You will find that with the heavy feeding juvie discus need to grow well that the substrate is going to trap lots of feed, poop etc which will work against you over time and really affect your water quality. Are you interested in some recommendations to the tank to help with keeping the tank cleaner while keeping the plants?
We are here to assist with any specific problems but also help you be successful with discus over the long haul.
Pat