ignment about the sonnet...help pls?

The ignment asks you to discuss three things: "convention," "formal structure," and "internal logic." It seems to me that your focus on themes is relevant to the first and third items on that list. For example, it was conventional in certain periods for the sonnet to deal with a relatively narrow range of themes, but poets today write sonnets on a wide variety of topics. And it would be difficult to discuss the internal logic of any sonnet without reference to the way in which the poem addresses its theme or themes.