betta tail

For a few weeks now, one of my boys has had what I can only describe as an air bubble on his tail and I was told it’s nothing to worry about, but I came down this morning and it’s more than quadrupled in size! He’s actively swimming and feeding, so it doesn’t seem to be bothering him at all...

Hi, I'm having trouble determining the tail type and coloring of this female betta, can someone help out? The first two pics are older, the other is from today.

Hi everyone, so I have had my Betta fish for approximately 5-6 weeks now and I have noticed a change in tail shape. When I first got him he as a square shape notch in his back tail and it was very smooth and I think just part of his build. However I have since noticed it has changed to a long...