Featured Image Pixellated

Hi guys,

I didn’t used to have this problem but recently my ‘featured image’ (the one that goes on the homepage slider and consequently also at the top of the post’s page) has been super low-res and pixellated. They’re always Hi-res images. I’ve tried resizing before uploading to make sure they’re not much bigger, have uninstalled all the image plugins, then also reinstalled them… I’m using the Simple Mag theme.

Thanks so much for any help in advance!

The page I need help with: [log in to see the link]