Lower grades meant zinc output dipped to 3,311 tonnes (t) from 4,414t in the third quarter, while an outage reduced pyrite production to 10.109t from 28,375t.
Lead was better, with production rising for a third-quarter running to 6,656t.
Metal recoveries improved, however, and revenue rose to £8.02mln, with gross profits of £3.45mln.
The group said October has seen a further pick-up in zinc recoveries to 48.3% (42%) though lead has dipped to 41.4%.
Issues with pyrite production have been resolved, NQ added.
Brian Stockbridge, NQ Minerals' chairman commented: "The continued positive trend in milled tonnes and metallurgical recoveries has dramatically improved financial performance at Hellyer.
“The company achieved record production in September, and we continue to realise improvements in the current month.“