I agree. I would only keep a single male. I have seen a group of 6 2M/4F that were thought to be 1M/5F. It was in a friends tank who had purchased them as a sexed group. They were kept in a 6' 125 gallon tank. Unfortunately, two of them kept fighting, to the point that one had an injured eye. After it healed the fish was returned to the tank and the fight resumed. When I when to the friends house I immediately realized that there were two males. For a fish that often seem very mild mannered, the males can be quite aggressive when dominance is an issue.
Depending on size, sexing can be done by looking at the anal fin. Both sexes have pointed anal fins, but the females will not reach the base of the caudal (tail) fin. Males, once they reach about 3.5" to 4" will develop an anal fin that will exntend past the base of the caudal fin.
Males tend to be a darker blue, but no always. The spots are something that all C. moorii exhibit, but more often when they are sleeping, stressed, or are fry/juveniles.