Rather than applying these three terms to the works you mention, let me differentiate them from each other.
Basically, the three terms refer to three elements of language creation: artistic license, language choices freedom, and subject.They are often used too loosely, because they all appeared more or less together in literary history.
The term “Modernism” applies to an aesthetic trend in a specific historical period: 1870 to WWII, approximately; its salient features are a self-reference to the act of creating art, an acknowledgment of the need to move away from classic influences and standards, and an admission of everyday artistic creation as opposed to epic or mythological standards. In other words, the modern artist may deal with common life, and does not have to restrict him/herself to lofty or noble subjects. The themes of Modernism, then, could include industrial advances, psychological inquiry, and social development. The definitive work is Howe’s “What is Modernism?”
“Realism” refers to the accepted low degree of imaginary or poetic language (in literature), or rather its absence, an attempt to reproduce common speech patterns, rather than, for example, iambic pentameter. It refers to everyday language use–clichés, standard colloquial vocabulary, conversational syntax and the like—itself rich in subtlety and nuance. An addendum to realistic language use was expression of feelings free from Romantic exaggeration. It is a term that describes a style of fictive discourse.
“Naturalism” refers to subject matter – real-life objects and environments rather than Utopian, fantasy, or imaginary worlds. As a retreat from the heroic worlds of European myth and ancient Greece and Rome, it was more appropriate for the burgeoning democracies of the 18-20th centuries. Heroes of Naturalism are characters whose human qualities make them special, not the blessings of gods, etc. Imbedded in the connotation of the term is also an appreciation of the burgeoning sciences and taxonomies – Darwin, Huxley, Linnaeus, etc.—the organization of the rules of the real, physical world we live in.