The subject of this paper are the relationships among the marked length spectrum, the length spectrum, the Laplace spectrum on functions, and the Laplace spectrum on forms on Riemannian nilmanifolds. The author shows that for a large class of three-step nilmanifolds, if a pair of nilmanifolds in this class has the same marked length spectrum, they necessarily share the same Laplace spectrum on functions. As well as he presents the first example of the pair of isospectral Riemannian manifolds with the same marked length spectrum but not the same spectrum on one-forms. This is the only example of a pair of Riemannian manifolds with the same marked length spectrum, but not the same spectrum on forms, outside of the standard spheres vs. the Zoll spheres, which are not even isospectral for dimension less than or equal to six. This extends the work of Eberlein, who showed that on two-step nilmanifolds, the same marked length spectrum implies the same spectrum both on functions and on forms.