Image slider – smaller images are being stretched?

Hello,

Recently, when i’ve been adding images to the image sliders, if there’s a smaller image, it’s being stretched to fit the space in which the slider is held?

But it’s only occurring on images i’ve been adding recently and not stretching old ones?

Do you know what this could be?

I fixed this on the homepage by adding in quick css

.page-id-433 .avia-slideshow li img {width:auto!important;}

but I was wondering if it’s a glitch in your side or maybe some settings i’ve changed?