Meteor Slides: slideshow won't center

https://www.annepouch.com/grla/

My client is saying he is seeing more white space on the right side of
the image than on the left and will I please center it.

When the browser is in “actual size” it looks fine but if you zoom out, I can see what he means
I have been reading all the other posts to the support forum for this and have tried a bunch of things to center the slideshow with no luck like

#meteor-slideshowhome {
margin:0 auto;
}

#meteor-slideshowhome {
margin-left:auto;
margin-right:auto;
}

.meteor-slide {
margin:0 auto;
}

.metero-slide {
margin-left:auto;
margin-right:auto;
}

and these:
#meteor-slideshow {
margin:0 auto;
}

#meteor-slideshow .home{
margin:0 auto;
}

#content .meteor-slides {
margin: 0 auto;
}

and nothing changes – however if I change margin-left to any number of
px it shifts to the right.

I am using a responsive theme – Genesis/Prose.

Thanks for any suggestions!
Anne