It was speculated that ethereum would hit its all time high if the upward price trend had continued, the uncertainty in China made altcoins to drop along with bitcoin, ethereum went even worse. I think situation changes in future making upward movements and people who invested can stay happy.
Downfall in the price is temporary and it will recover back soon so if you have faith in potential of ETH then I think you should start investing in it as this is the best time to get into ETH.