The problem is seen here: http://aivarasdaukantas.lt/demo/#tf-naujienos (the second post)
Thumbnail size is set:
set_post_thumbnail_size(250, 165, array('top','left'));
It doesn't seems (from the name of your pictures) that you're using the thumbnail version in your template, but the full version instead - they're just stretched with the use of the height and width arguments.
I suggest to use the_post_thumbnail in your template to get the thumb version of your image:
<?php the_post_thumbnail(); ?>
Maybe need regenerate thumbnail ?
Try this plugin "https://lt.wordpress.org/plugins/regenerate-thumbnails/"