Homepage post thumbnails are different sizes

My website homepage “New posts” thumbnails are messed up…
The 3 featured images are the same size (1100x688)

My website: www.cavamedios.com
Picture: http://imgur.com/a/6jTuM

How can I fix this? Thanks in advance!

Also another question…
How can I hide the post name in the homepage?

Same website: www.cavamedios.com
Picture: http://imgur.com/a/uXuJh


The first image’s thumbnail wasn’t generated, so please delete that image from media then edit the post and re-upload the image after clicking on Set featured image from the post, so if you do that way and you won’t select an already uploaded image, the thumbnail will be generated and it will be the same size as the other 2 images ( which are the correct size ).

Best Regards,