I got something like that but it said "you are only partially responsible for their deaths" or something similar. I'm not sure what that means though...
I think it means how you interacted with the characters, but each of their deaths was only kind of your fault, since Monika was the one who did the most damage. Like, you were the one who persisted in trying to get their endings, so Monika is kind of blaming you? I don't know.