Images not sizing down correctly when using theme

I just started using this theme yesterday. I noticed when previewing the theme that it made my images their fullest size (even though I had sized them down), but I assumed it was just a glitch with the preview and the images would be the way they were supposed to be once the theme was activated. I activated it and I’m still having the image issue. They’re all much larger than I want them to be, sized at normal rather than sized down several percentages as I made them. I wasn’t having this issue with other themes and haven’t installed anything new or changed anything regarding image sizes on the style sheet.
Can this be fixed somehow? I’m worried about using the theme because all of my part entries have many images sized down.