Block search engines and AI from just one of my blogs

I have three blogs on Micro.blog and I want to indicate to search engines and AI that they should not index one of them. I do not want to block search/AI from the other two. Is there a plugin that will easily allow me to do that or do I have to use a custom theme? I realize that all of this is on the honor system, and if search/AI wants to ignore robots.txt there’s nothing I can do about it. (Or is there?)