External style sheets - HTTP requests - SEO

Hi,
I am trying to optimize my website for better SEO and I have found that there are 12 external style sheets and 6 external java scripts. This is causing many HTTP Requests and slowing down the site.
Are all of the style sheets being used or is it do do with the many themes? I have removed the different theme colours and only kept the one I am using - Teal, but there is no improvement.

Any idea what I can do?

Thank you
Maria