Tifa's Ventral Fin

[metalbetta]

I highly doubt there's a huge issue going on, but this was something strange I noticed last night.

When Tifa, my HMPK gets all flare-y, he does the usual stiffening up, showing off one side of his body, darting back and forth, all the fun stuff bettas do.
BUT, I noticed last night when he was doing his thing that one of his ventral fins was moving around while one was just hanging there.

I'm not sure if this is normal or not or if this is a problem with his fin, i was just wondering if any of you have seen this in any of your bettas. I'm just an overly paranoid person when it comes to my boys and girl doing things that are overly weird. I mean they're weird enough!

As a side note, when he's relaxed he's able to pull both fins back to his body just fine. it's just when he's flaring he does this.

Thanks!