I have now switched to antpool and it is mining OK.

The fastest I can currently get out of any S9 is 12-13THs. 

I have found that with quite a few S9 they only run up to around 7THs at default frequency (650), however, when i turn them down to 625 they come up to 12-13THs.

Has anyone else experimented with the frequency?  Have you found any particular frequency to produce better results?

Thanks guys.