Hello Stefanie.
I do think that you have a male, the band in the caudal is not to be seen in females.
The behaviour you are talking about with the one female, well … I think that if its spawning behaviour its a good suggestion that theres a male in the tank. Females alone will not do that.
I have found that if you keep more fish together the courtship between one female and one male is a bit prohibited, – it will occur, but if you seperated the pair it might show up much more clear. So if you have a feeling that theres one female showing courtship behaviour, let that one female be the only female with the male, and see what happens. With one male, you also really might want to make sure that there is offspring 😉 – and this is much more likely to happen with just the one pair in the tank. Two extra females is going to make it difficult.