File Size for Theme is Unusually High – Not Sure Why

Of several themes I’ve developed I’ve found that one has an unusually high file size – like around 500MB. Others, that look on the surface like they’re of a similar size, are 10 times less than that. I have removed excess plugins, made sure my media library only contains files being used, removed themes not being used, made sure post revisions are not saved in my wp-config, etc… and still the file size is really large. How can I troubleshoot why that is? Is there a tool that will help with that?