Image Quality Loss

I am working off of the Virtue theme (free version) and I’m having trouble figuring out why some of my images are losing quality once they are posted. For example, on my homepage:

http://www.themrhusband.com/

The main hero image of the house and icons is a little blurry and the color doesn’t match what I created it as in Illustrator.

Additionally, all the thumbnails for posts under the section “Recent Posts” are pretty pixelated, but the image file loaded into media library is not.

I suspect WP or the theme I’m using is applying some sort of further compression but I don’t know how to stop it from doing it.

Help?