That's because profitability crashed and miners have abandoned it. It was a nice run while it lasted.
Bitcore has an issue I believe, history for the last 5 hours was about 1 every 50ish seconds, now we are at 20+ minutes. Checked a few other pools noone grew exponentially in hash power in the same time (not saying that is end all be all)
Actually jwarren81 there was still PLENTY of hash power, it jumped after the lack of blocks flowing, it was the difficulty grew from 128 to over 710.