How can there be a different page load speed of two identical sites?

Question

1C-Bitrix

Good afternoon. Such a problem. The site was developed on Bitrix. After development, it was transferred from domain to domain. And the site started to work very slowly. Both sites are hosted. There is a lot of space for hosting. Hosting settings for both sites are the same. I can't figure out what could be the problem. And I also noticed that
on a domain where the site loads quickly, images in the developer tools are loaded only from the page on which I am.
And on a domain where the site is slow, all the pictures are loaded on all pages - from the entire site.

Answer 1

You only write loan agreements)

The site was developed on Bitrix. After development, it was transferred from domain to domain. And the site started to work very slowly. Both sites remained on the hosting

At what point did they become two?

from domain to domain

Those. in fact, the site remained in place, only a domain alias was added to it? And so there were two of them?