Post Thumbnail being cropped

I’m having some trouble with a discography plugin. I modified the album size to 350 by 350 by using an array in the_post_thumbnail(); When I upload an image as the featured image with the dimensions of 350 by 350, the image get’s cropped horizontally in the middle. Would anyone know how to turn this off, maybe in functions.php or in the plugin itself? It’s the Musopress Discography plugin.