My effect sizes f-squared are small and p values are significant. Is it correct to say that the independent variables are poor predictors of the outcome variable when mediated by the mediator? I just don't know how to put it into words.
As long as the mediating effect is significant, then you can say that your mediating variable has the mediating effect (p value) and state how much the effect. Now, to judge the value if it is small or large, it referes to the type of relationships and variables being tested, as well as how these variables are compared to what is in the literature.