Vina Theme – some thumbnails cropping image

Hi there
I just installed the Vina theme which looks great but I seem to be having trouble seeing my photos in their complete form in certain areas….in other words I am only seeing the top left of the photo when the photo is made into thumbnail.
The link is https://www.edenweb.net
For example if you click on GO GREEN you see the archive version (thumbnail) of the photo and you only see the sky of a hot of the sky and the ocean…I have fiddled with settings in media but that didn’t seem to help at all. The picture I uploaded is 250×250.

One more thing…I want to make it so that the front page ALWAYS displays the latest story in a certain category and not always the latest post…is this possible?