I don't think it is ich because I don't see any white spots but the ER mods will confirm. It could be velvet from the darting that you describe and the clamped fins. Flukes are less common and I will let the ER mods again comment on that.

Keep in mind that I believe one of those products is actually stronger than Rid-Ich and needs to be used at a half dose. Please check in here before you use any of them and the ER mods and other betta experts will give you some good advice.

I know it is difficult when they don't seem to be feeling well so sending you both good thoughts.

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