yep two things... one: EEs can lay any color of egg, including brown. It's more common than you might think. I know a couple of people who were expecting a blue or green egg and thought their EEs weren't laying, but then they caught them in the act and they were just laying brown eggs! EEs are cross-breeds and can have many different gene combinations.
two: my EEs were all my earliest layers. 19 weeks 6 days was my first egg and it was from an EE. All 6 were laying by about 22 weeks. However, like I said... they have so many different gene potentials, depending on who is breeding them, that maybe you just have some that will lay later. Watch to see if any hang out on a nest and then you get brown eggs. If not... I'm sure they'll start soon! Good luck to you!