Photo size for slider..after update plugin, photo's seem too big..how come?

Dear all,

I finally managed to update my Revolution Slider. Somehow, with this latest version, the layout has changed and some photo’s seem to big. The homepage slider should be auto responsive and fullscreen. Some photo’s are 1920 x 1440 and seem too large while some don’t. Strangely enough a photo size 1440 x 1080 also appears to be too big.

I have other sliders on almost every page as well and some photo’s seem to be too big as well since I updated revolution Slider.

My website: http://www.bastarto.com

Is this solely a matter of decreasing the size of the photo’s or should I add something to the custom.css? I absolutely have no clue.

Thanks in advance everyone!