Right, I agree. The last fish swimming from the right to the left is probably a sumatranus male. The others are not as clear as this to be seen.
Females in principle have the same black dot at the end of the dorsal, but often it is subdued.
This private import might be a mix, that’s a problem. Nevertheless: P. sumatranus is very rarely traded. You should definitely buy the individuals that are most clearly to be recognized.
And since it is a private import, Helene’s hope to meet them in Kopenhagen (or ours in Germany) is not very likely. Sorry to say.