Naomi,
I would think that what is happening is that as the project is being rebuilt it is picking up references to all the classes etc that are referenced in the other apps. This is hard to track down. If you reference one prg, scx, vcx that is used in another app and it references something else used in the other app the whole thing will daisychain and you will end up being huge. I don't have a solution other than being very careful to limit the way that code references other classes and resources.