Alt tags for featured images not showing

I just began working on this site which has a custom built Genesis theme.
I have been adding missing alt tags to images and they show when viewing in blog format, but the alt tags do not show in the page source when viewing individual posts or pages.

Yes, 80% of the alt tags are in there, but I suspect the code used is not set to show the alt tags I have put in.

function iamp_featured_image() {
	if(is_single()) {
	$imgsrc = iamp_get_featured_image(get_the_ID(), 'large');
	echo '<img src="'.$imgsrc . '" />';
	}
}

Any tips or ideas would be appreciated to get the alt tags to show in the page source.
Here is just one of the posts:
http://www.geniushr.com/sex-marriage-effects-employers/