The same company is behind all of these. They live on separate domains because they serve different audiences, not because they are separate businesses — so if you have an account with one, you are already dealing with us.
Every one of these is operated by Astrava UG (haftungsbeschränkt) in Lübeck. The company details, and who is responsible for the content, are the same on all of them — they are in the Impressum.