I have a problem with featured images on my page. They are displayed differently, as you can see here: http://sfcentar.com/afroexp/category/zbirka/
I don't have any clue what's going on. Posts with 300x250 images have been posted last month, the smaller one today (although his featured image is also 300x250). Older posts were posted before as Portfolio posts (used with Portfolio Press theme), so I tried to convert last post to Portfolio and back to normal post with Post Type Converter plugin - no effect.
Does anyone knows what is going on here?