Yeost SEO Plugin causing sitemap error

Hi,

I recently had my site changed from http to https and since that change my yeost xml sitemap is now showing an error in Google.

Your Sitemap or Sitemap index file doesn’t properly declare the namespace. Expected: https://www.google.com/schemas/sitemap-image/1.1 Found: https://www.google.com/schemas/sitemap-image/1.1
Sitemap: https://www.aging-naturally.com/post-sitemap.xml
Parent tag: url
Tag: image

According to yeost this error is impossible to fix with their plugin. So, I am wondering should I deactivate this and use another xml sitemap. I may have the same problem but I might be able to fix it?

I asked my hosting company and they told me how to fix it by replacing a line in the opening tag. But I have no idea where to look and not sure I can if yeost say it is impossible to fix.

Any help will be greatly appreciated.