Size of Featured Images for Projects

Hello, I wanted to reduce the size of the featured images for projects that are displayed as thumbnails on my homepage monirahaa.com In order to do so, I typed the following in "Additional CSS:

.portfolio-wrapper img, .featured-content-wrapper img, .archive-posts-wrapper img {
	width: 70%;
}

While this worked when I'm logged in, there is no change when viewing the live site. Any help would be appreciated. Thank you in advance!