I would only trust the reading directly from the actual mining software, and not Nicehash's website or GUI. Those (especially the one from the website) will almost always vary from your actual hashrate.
I also experienced a significant drop in hashrate since a few days ago on Equihash, with my GTX 1080. It went from 475~480H/s to 410~415. TDP also went from 110% to 80%. The hash rates were taken directly from the console windows, and I would love to know what caused this serious drop.
That was probably due to that TDP drop, if you're mining Equihash, you're just better off using EWBF, its better hash rate wise and it won't take alot of fees. Plus you can mix and match you're overclocking to match your desires.
(Windows 10, Nvidia GeForce GTX 950M)..
It works on my end, If you're over clocking your card try it at stock clocks for a while then gradually build up to your overclocking setting.