Hey Matt, welcome, gorgeous fish first and foremost...
I don't really see much evidence in the video you posted.. Do you have any other pics or video to support what you report? I was going to say the fish looked like it was shimmying or almost doing a mating shake...
You said you see "Not eating, Clamped dorsal fin, dark eyes, stress bars, tailstanding, bit of white fin tips."
From what you post and report, nothing stands out as an obvious issue. You add prime or a dechlor to your water? Can you think of anything that changed or could have happened in recent weeks? Have you kept the same routine up to grow them?
The best advice I could give now would be to increase water changes and see what happens, keep up with the salt it cant hurt. None of the other fish seem to have any issues...
I see some tank mates there, what is the deal with them? When added and all that? Def, no cross contamination or anything of the sort?