ᐅ Experience with mold-resistant additives?

Good morning everyone,

We are currently renovating the bathroom because we found two dark spots. The suspicion that there might be mold behind the wallpaper was not confirmed. Apparently, it is only on the surface of the wallpaper (which was painted very thickly in some areas).
Still, I wiped the plaster at these spots with Domestos. The ceiling is suspended with drywall panels.

About the surroundings:

One window, no blinds. Shower and bathtub.
Tiles go up to the door frame, beyond that there is wallpaper.

Now my question to prevent such issues in the future:
Is it worth adding an "anti-mold" additive to the paint? A few extra dollars wouldn’t be a problem, and I would feel more comfortable if the wall was treated with a fungicide but still breathable.

What product would you recommend? Alpina White? Paint from a professional painter supplier? An additive from Mellerud?
According to laser temperature measurement, there are no thermal bridges at these spots (at least nothing localized).

I would really appreciate your answers and thank you in advance.

Best regards,
Daniel

There are interior paints with ready-made FA settings available in specialist stores.