Keeping a whole bunch of 12 week old does around is a risk. They most definitely will become hormonal and the buck will most definitely start establishing himself and thinking about breeding. While they should be bred closer to 6 months they sometimes will breed much earlier. I've had kits out of 3month old smaller breed does. A 3-4month old larger breed doe getting bred would not be a shock. All previous times I've had trouble was when I had a bunch of 10-14week old does hanging around I hadn't gotten to butchering. They can make the mature doe territorial, the buck territorial and wanting to breed, they can get territorial with each other and younger kits... If you want or need to grow them out to that age I would suggest a 2nd colony or growout pen. I was having problems in 12x12'. With the divider down and back in 12x24' our problems mostly went away until we ended up with a bunch of 6month old does having their first litters. I think all the new mothers plus the bucks getting excited over breeding them again is what set off our second round of aggression. Now that the does are on at least their 2nd and 3rd litters they've calmed down a lot and so has everyone else. The bucks still get stirred up when a doe is ready to be bred again and the does still get territorial when nesting but aside from an issue with enough nesting sites and space around them (we are culling an adult doe before another round of litters) the problems have gone away again. Young does are just trouble if you crowd them at all and one of them can claim 1/4th of our 12x12' stalls if they get it in their head to do so. Then the bucks get set off by the maturing does.

I'm just curious about putting the bucks in with the does. I've always been under the impression that if you take the buck to the doe she can get territorial and hurt him. Does it work in a colony setting because the does have more room to get away from the buck than in a cage?

Typing all this on my iPhone is making my eyes go all wonky!

Actually introducing bucks is the easiest part. They are not a part of the doe pecking order. They exist outside of the rules the does set up for themselves. The does will charge them at first but the bucks just turn around and hump their heads so the does give up after a few minutes and learn not to bother bucks in the colony. Instead there is just a lot of squeaking, grunting, and running away or flattening when a buck approaches and a doe doesn't want bred. Aside from the occasional grooming and the usual "this is my food container area right now" the does and bucks don't interact beyond the bucks checking if they can breed a doe and a doe agreeing or making a ruckus.