You might want to edit your profile a lil bit to not give so much info away.
It sounds like you've embraced a really diverse bunch of people, and that's great. The flip side of that is sometimes people don't feel they have enough in common with each other and if people don't "get them" as they wish, they feel like they're being dissed.
If there's a sisters living in house/living out of house disconnect, make it a point to get together at the house before going to mixers or other campus events and arrive there as a group. (No, I don't mean pregaming.) If everyone just kind of "trickles in" on their own, there can be people who don't speak to each other all night.
Try having seating charts at meetings so different people sit together rather than the same cliques being together all the time.
I'll think of more later.