Don't worry. My first interview was on February 10 and the second one on March 3. Three-week lag is a reasonable estimate.I had my first interview about 2 weeks ago and still haven't heard back. My status has been "Application Under Review" since.
From what I could gather in different forums, there is a 3 week lag between the first interview and hearing back from UCB !
Maybe RainLee can confirm this.