Weve seen the network difficulty spike starting July 2017 to October 2017 with all time high of 30T. This is a killer difficulties for small-med size miners. Imagine a gpu with 30mh/s will earn 22/USD a month... this is truly non-profitable.
However after the byzantium update the network difficulty level drop to 15T, which is good. Meaning, miners can get more coins in the process.
Is this a glitch after recent ETH update?