As far as the hardly visible band on caudal fin goes, my new fish show this too. One of the males has a clearly visible band. Two others have almost adult coloration on all other fins but the caudal and the rest of the males can be distinguished only becouse of the green/blue edging on the caudal and other fins. At the beginning I was even worried that I could possibly have some mix of species but couple days later another male started to show thin band that is now looking almost normal already and I have seen another developing band on the other male. It seems like it takes some time to develop a full coloration as the fish are maturing. I have seen quite a lot of species where developing full adult coloration takes some time even after the fish are already sexually mature. So I do not panic anymore. It looked exactly like onthe very above photo.