Issues removing image borders and shadows

I am having issues with images on my main/home page. I have changed a bit of css already and solved most of the problems but if I put a post up as an image post, I get this approx 5px white border and a shadow (only shows on home page, not post page). Posts using featured images do not have the border and shadow (as I have removed that already). I just can’t seem to figure out what/where to change.

My site is https://mikaihh.com the first post showing (large photo) is the one with the border/shadow I’d loved removed.

Thanks in advance.