I needed to make a new image size* to use for the links on the Baking Portfolio page, and I ran Regenerate Thumbnails after that, so it seems that actually creating the new images finally righted the rest of the thumbnails as well.
(For reference for future users, that’s the add_image_size() function, which goes in the functions.php file. I made a 222px by 222px thumbnail called “portfolio-thumbnail” that cropped instead of resizing, with this code:
add_image_size( 'portfolio-thumbnail', 222, 222, true );
)
@Sakin , your tip for the Slider worked great. It didn’t work for me to change any option on the Theme Options panel, but once I changed the post IDs for the Slider, it worked. Thank you so much!