Lymphocystis, from a hobbyist's POV is an infection. Typically it isn't lethal, but it can grow on the side of the fish's flesh like cotton. It can eventually just drop off the fish, like it did on my Copperband Butterfly that I had in quarantine for about 5 weeks.
The problem is if it grows around the mouth area. As it grows larger, it will block the fish from being able to catch any food. This happened with the fish mentioned in this thread. So I had to actually catch the fish, put it on the table, trim/pluck off the stuff, and apply a drop of Lugols to the area for a few seconds before putting it back in the water. It doesn't take long, but it is a little unnerving.
I don't know what causes it as I never did that much homework or perhaps I've simply forgotten since then. Your comment about it being a newer fish may refer to the age of the fish more than the purchase date. If you have a sick fish, you need to treat it rather than wait and hope it goes away.