Flaring doesn't necessarily mean they are angry or showing distaste. It can mean each one wants to show off their beautiful fins to you, like mine doesYeah time to time, just give him a workout.
My guys always flare at me when I walk past, I don't think they like me very much. ._____.;
yea i do that too but i never put the mirror in the tank coz it might have come in contact with something else before so i put it against the tankI put a floating mirror in my bettas' tank once a week for a few minutes, just to exercise his fins but make sure to not stress him out. It's very cool to watch.