Hello, your post wasn't in English, so I can't read what your wrote.
The fin on the Banggai, where it terminates in a nodule, is a pretty common reaction to fin damage. I've seen that quite often. As long as the fish are still eating well, and not breathing fast, I don't worry if I see that.
Translation
Got 3 banggai 1 month ago, two of them had broken fins when I first got them and now they all have this problem, will it grow back? Will I need to take any medications? They are eating hatched brine shrimp and one of them recently started eating pellets. Thanks.