It's easier to look at their hashrate chart, but the diff chart will work too.
Note that except for one "single-day" spike on April 26 that was probably LUCK driven (might have been folks on auto-switch miners bouncing out of ETC or some such though), the Ethereum Total Hashrate (and difficulty) has been slowly DROPPING since April 16.

Yes, there was a big surge for several months before that - but the surge is OVER unless Ethereum price starts rising.