Hey there,
great tool! SecurityTrails has a great API available for querying the information you are currently scraping from the free app. The free app regularly changes and the method you are using will not work in the future.
Our API is free of charge for your use-case and fairly easy to query, please check out
https://docs.securitytrails.com/reference#history-dns
In case you have questions, I will be around to help you switching over ;)