Forking rule: «REQ - 7 Difficulty adjustment in case of hashrate drop In case the MTP of the tip of the chain is 12h or more after the MTP 6 block before the tip, the proof of work target is increased by a quarter, or 25 %, which corresponds to a difficulty reduction of 20 %. (howtotoken.com)
The recent drop in hashrate on the mining pool can be attributed to many possible factors, yet some people feel Antpool needs to switch (bitcoinist.com)
Huobi, BTCChina, F2Pool, BW and Antpool remind the bitcoin community that they account for the 60 % of bitcoin hashrate in the world. (coinfox.info)