Elegant post style big preview images are cropped vertically

Hello
I’ve looked at lots of posts and tried a bunch of things. I’m using the elegant blog setting in a full width page.

I need all of my images to be their native width and height values, from masonry grid thumbnails (working nicely!), to single post featured images above the post text. Please advise and thank you in advance :)

css –

#top .fullsize .template-blog .big-preview img {
    width: 100%;
	height: 100% !important;
}

.big-preview img {
    width: 100% !important;
	height: auto !important;
}

.html_elegant-blog #top .big-preview img {
    width: 100% !important;
	height: auto !important;
}

.html_elegant-blog .entry-content-wrapper .big-preview.single-big {
    width: 100% !important;
	height: auto !important;	
	margin: 10px 0px 30px 0px !important;
}

.html_elegant-blog .entry-content-wrapper .big-preview.single-big img {
    width: 100% !important;
	height: auto !important;	
	margin: 10px 0px 30px 0px !important;
}

.single .big-preview {
    width: 800px !important;
    height: auto !important;
}

I set the media settings to 0 for all three and it didn’t make a difference, so I set it back to my other settings.
I could install the simple image sizes plugin but this site has a huge image library, and I don’t want to ruin what’s already there.