Coraline images in post won't resize

Changed to the Coraline theme which is great except my images are all crazy big. I can resize them while writing the post, but on preview or publish they don’t resize down to what I saved them as in the draft/post.

There’s got to be a code somewhere that I can change, these take up the whole page in preview/publish but are at 70% of 300×300 while in the composing screen.

And all the images I had on my blog before switching to Coraline are now bigger than what I had them as on my old theme.