What made you concerned about the fins?
The only thing I can't tell from a still photo is whether or not the fins are soft and flowing or whether they are more rigid, stiff.
My niece had a betta that got sick, his fins looked fine except they didn't move much as he swam around.
Doing a quick test holding up a mirror is he able to fan everything out still?
Not for too long though, it will stress him out !
Behaviour sounds perfectly healthy though, I'm just curious what your concern was.
Very pretty colours btw.