@stacyduval, JetPack is supported at a separate website. We volunteers here at WordPress.com have virtually no knowledge of the plugin. Head over to http://jetpack.me/support/ and they should be able to help you out with your styling issues.
Try making the CSS more specific. One way might be to use a very strict selector, another would be to use the “!important” rule (although best practice says to avoid using !important if at all possible, sometimes it is warranted though).