Corrupt root url for all media files

Hi all,

I am an intermediate user of WordPress I just upgraded to 4.7, and also did a few other SEO enhancements following recommendations online. Having finished, all my media file urls had been altered from “https://neuchatel.co.nz/wp-content/uploads” to “https://media2.mydomain.com/wp-content/uploads”.

I have tried several search and replace software unsuccessfully to find and replace the erroneous urls.

I have traced the problem back to an attempt to parallelize my content using code at the bottom of this page: https://stackoverflow.com/questions/34404336/how-to-parallelize-downloads-across-hostnames-on-wordpress/34404337#34404337?newreg=de27863552434268bda29efbbad1cd04

I installed the code in the functions.php file, and the code crashed the site so I removed it. But somehow all my media file urls had been changed as per the code in this page.

Any advice? Thanks in advance!