A side profile shot would help determine ducks lips (or not). it progresses very quickly, and if you try to manually try to close the jaw, it doesn't move.
At first I thought my beani had a simple jaw dislocation, that can sometimes be snapped back in place, it would not.
Lowering the temp stops the bacteria from multiplying exponentially, and gives the fishes immune system a fighting chance to work, at 82'F or above the bacteria easily overwhelm.
here are some shots over a few days
at first a small separation appears around the lip

the gap gets larger, and so on, as the bacteria continually destroy inner tissue

I find it is always better to let your fish starve while on vacation, the only time I've had death is when I let someone else feed. Amateurs always feed to much, and have no clue about the seriousness of degrading water quality.