Around 3 AM on July 6, 2018, I noticed my valid shares on Ethermine were down and my effective current hashrate dropped a lot. Also, the consoles on my rigs were reporting the connection to Ethermine was lost. I wasn't the only one. I'm not sure what happened, but everything seemed to be back to normal later that morning.
While Ethermine was having its issues, I decided to put all my rigs on Nanopool. Last time I used them I made less ETH and this time was no exception. My rigs have been mining on Nanopool for the last 60 hours and I've only made as much ETH as I would have made after 52 hours mining on Ethermine.
Maybe I just have bad luck with Nanopool. Others who have tried both pools have had better luck with them when compared to Ethermine. Whatever the case, I'm switching everything back to Ethermine today.