with the new version of illustrator layers that are turned off (and not visible) still push the bounds of the white area that is shown when exporting.
If the visible sub-layer is smaller in any direction than a turned-off sub-layer in the same parent layer then there will be extra white space when exporting using the "save for web" function.
This wasn't the case before the newest update of illustrator. The workaround right now is not have images share the same parent layer if they are going to be exported separately, but invisible layers should not be affecting the image bounds.
Am I missing something or is this just a really funky quirk courtesy of the new update?
Sorry to hear about this. Would you mind sharing the version of the OS & Illustrator? We'd also appreciate if you can share a small video of the workflow. It'll help us understand the issue and assist you accordingly.