So decided to upgrade my units to use the extranonce patch at westhash/nicehash.

 
To cut a long story short:

-Step one was to upgrade the firmware to antminer_S320141126.bin. The result was: my units mined perfectly well on AntPool but on any other pool including Westhash, they dropped below 100 GHS.

- I tried most of the suggestions on the Bitmain discussion thread and elsewhere...but to no avail.

- In the end, I went back to original firmware. While doing so, one of my S3s got stuck for about 30 minutes while i was flashing it. Now i cannot connect to that S3. Even the reset button did not help me. That S3 is now incommunicado. Luckily, I still have 2 weeks left on its warranty and can likely do an RMA.