Oh my goodness! hehe! Here I was thinking about what could be wrong, vega. That's certainly possible that those black edges are normal coloring.
I bought my blue gourami (three spot) last week at Wal-Mart, and over the last week in QT
, he has been brightening up A LOT. His colors are getting much bolder than when I bought him. I just went down and looked, and the back edge of his bottom fin is black!
No black on tail or dorsal fin, though.
A pic would definitely help. I don't know that I would assume for sure yet that it is natural, but if it is, that would certainly be great!