Custom Theme Drop Down Menu

So I am working on a custom theme, and i got the menu working fine…
http://i.imgur.com/u8yvwRs.png

However, when I add a sub-item (with the intention of it showing up as a drop down in the menu) http://i.imgur.com/zJLNC7B.png

the menu breaks and looks like this:
http://i.imgur.com/R5Ytsgq.png

I’m not even sure why, nor how to fix it… Can anyone help?