Update:
Still running errors free at 750M. Hashrate stays even but Zencash mined per day has dropped a little to 1.35 Zen a day. Probably due to new Z9s coming online. Getting closer to ROI.
Which pool are you mining on? i'm only getting around 1.05/day zencash on Zhash.pro while cranked to 750.
Also I think there's supposed to be an upcoming reward decrease for ZEN soon if it hasn't happened already