Won't be dogmatic, but from the video I have doubts that it's simply a quirky behavior. Kind of a quick video, but I think I see him twitch, like a response to an irritant. At least if it was me, I'd believe something was wrong and attempt to treat, like you're doing, and hope with his apparent alertness and energy it's early enough. Wish I could be more help than that.
The twitching and the rapid mouth movement/spitting seems to indicate something is irritating it. It could be anything from flukes and external parasites to something in the water. Have you sprayed any pesticides recently or cleaned near the tank? Any painting in the house? Any new decorations or plants? Do you have a conductivity meter to check for stray current in the water?
Stray voltage from the lights? Or in combination with the heater?I have played with the lights over the last few days though and there's definitely some correlation with it. With the lights off his colors are normal and tonight I saw no signs of twitching or whirling over the course of a couple hours. Lights on and instant darkening of colors and the whirling began within a few minutes.
Here's the vid.
https://www.youtube.com/shorts/FXdgylmeJTc