Use https://api.blowfish.xyz/openapi/ instead.
You can use these specifications to generate a diff of exactly what changed between the version you're currently using and any other version you might want to update to. To do so, you could use the following command after downloading the spec's locally:
diff ./v20220601.yaml ./v20230308.yaml
Replacing v20220601.yml with the version you're currently using and v20230308.yml with the version you'd like to upgrade to.
Note: To see a side-by-side diff, add the -y flag before the file paths in the command above.