Did you cycle the power before this happened? In a BFL 65 nm device, you'd  like see a drop of more than ,1 GH/s if you had a blown core. I've noticed that the hashrate can differ by 1-1.5 GH/s after powering it off and on. After several hours, it often climbs back up to the usual rate, but sometimes sticks at the lower rate for several days. I then try cycling the power again if it annoys me, but this can leave me with the lower rate that annoyed me. About the only thing you can try is 1) wait a while, or 2) cycle the power. If it were to drop to a steady 54% you could contact them for an RMA, but for a less than 1 GH/s drop, they would likely say the same thing I am. Coincidently, I got this same suggestion from their tech support several months back due to a similar issue with my 50 GH/s unit. Good luck.