I've noticed my Jabu-Jabu had almost the exactly same thing you're describing for your female. One of his ventrals is long and perfect, white tip at the end. The other was curled up and seemingly destroyed but now that he's been with me for a couple months, it's like it's tried to grow back. Instead of growing back normally though, the destroyed fin is still there and it's like there's a whole other ventral fin growing from it starting with a white tip.
Doesn't stop him from getting around or blowing a ton of bubblenests and otherwise seems perfectly healthy. I just won't ever breed him since that could be a mutation or health defect.