Even in a strong market such as now, investors have to watch out for weak action. AmTrust Financial Services (AFSI) had a tough week last week. But Jazz Pharmaceuticals (JAZZ) rallied for a third straight week. AmTrust, which broke out on the Oct. 21 follow-through in solid volume, erased a 16% gain past a 46.12 buy point from a double-bottom base. The round trip of a double-digit gain marked a sell signal.