Hate to agree but thats definently a female. Tub is thick, flat on the end, and abit to the front. Everyone makes mistakes and Jeff still is arguably the best C/SA distrubutor period. The same happened to me when I ordered 3 male Citrinellus and 1 Female. Instead I ended up with 3 Females and 1 Male. Females all were build pretty solid and the one I kept's hump she would get right before spawning would put the male's semi-hump to shame. She ofcourse would loose this after they would breed. Females can have their tubes down for a while and it's not always instant that you get a breeding. Especially since your Amphilophus are still Juvi's and haven't bred yet it ussually isen't instant, though my pair did a couple of weeks after getting them. Both were 6"+.
Would also like to add I hate when people use the term "KoK" for "non flowerhorn" cichlids.
Would also like to add I hate when people use the term "KoK" for "non flowerhorn" cichlids.

lol, j/k. Just annoying as pure cichlids have scientific names and terms while man made hybrids have slang terms that refer to them. Just personal preferance and annoyance.