I dont know what the issue is. People say put them together as weanlings, I dont. When I want to start a new colony I just grab two girls out of the female growout bin and a male out of the male bin and stick them in a tank together and let the magic happen.
Same here. I never have aggression between my adults. However, I experience trends when the breeding groups go on dry spells or cull most of 2 week old litters. Very strange AND BLOODY!