Strange thing happening with a soft focus rollover

Hi

I have a strange issue an image rollover instead of sitting on top or behind the image it sits below. I’m pretty sure its a CSS issue. Any ideas anyone at the moment it has two images one out of focus and one in focus that should be sitting on top of each other instead of adjoining vertically as they do now. Look at the post thumbs on this page.

https://bmc-client.co.uk/commercialbiomass/news/

Any ideas anyone?? Many thanks in advance