They are the lords and owners of their faces, (7)
What does it mean to be the "lord and owner" of your own face? Doesn't that sound like you have the ability to control it, to keep it from showing any emotion that you don't want the world to see? And if you're trying to show something different to the world than what's on the inside, doesn't that make you hypocritical?
For sweetest things turn sourest by their deeds;Lilies that fester smell far worse than weeds. (13-14)
Even though they don't say so explicitly, the context of Sonnet 94 as a whole makes it a safe bet that these two lines are actually about people. Basically, they are both saying that the most beautiful people turn into the ugliest people of all when they do ugly things. The question is this: when beautiful people do ugly things, does this mean that they have changed their nature and become ugly, or is it that they were ugly all along and just happened to have finally spilled the beans? Either way, they risk hypocrisy.