plugins and widgets css files

Can someone tell me where to find the css files for the widgets and plugins I installed with my theme? I am trying to modifiy the look and feel of the theme BP-Social but so far I only manage to work with the base.css and core.css.

Understand that I am also adding widgets and plugins as I go along and not just using core stuff so a general idea of where to find them will be a great help

Thanks