Different sitemaps for two languages in a WP Multisite

Hello all,

I have a WP Multisite install with three sites.
Site 1 is total site in English
Site 2 is total site in Spanish
Site 3 is holder site (used as primary domain and redirects with a hack to en or es site).

The sites are installed in subdirectories (/es/ and /en/)

I have installed Infinite SEO.
The sitemaps for the seperate sites seems not to work. I only get a URL of the XML file to the English version. The Spanish version doesn't show up. I want to have two XML files for two different languages.

Any idea how to fix it? Or use Simple Multi Site Sitemap instead?

Greetings,
Jonathan Fokker