So, you have 6-7 birds in 8 square feet. That doesn't give you much room to put in hiding places. Remember, the space taken by feeders and waterers as well as hiding holes subtract from your available space. They might be a little crowded, which is not going to help. You want to have a...
How much space do they have? Do they have plenty of places to hide? It sounds like you've had some bad luck with all of the really aggressive boys. It is spring, though, and mine are getting more aggressive too.