Top 2 definitely males, and the bottom, more than likely a female. The pelvic fins are a little long, but does the belly have some pink on it? If it's got a pinkish belly, it's definitely female.
Actually, you should rething the ratio. If it's only 1 female with 2 males, she could get very stressed. Should be the other way around. Or if possible, you could get 2 more females.