This is all part of BCH's shitty difficulty algorithm, and how it impacts miners switching back and forth.
http://www.reddit.com/r/Bitcoin/comments/6vxbse/we_may_have_to_accept_higher_fees_until_september/The short of it is, the oscillating difficulty adjustments on BCH's side flip miners back for a few iterations, until the difficulty adjusts in BTC to a much lower rate - which will kill any incentive to mine for BCH. This is a self-reinforcing loop, which puts a lot of downward pressure on BCH price.
So, thanks to Jihan the asshole and Roger the dickhead, we'll have to go through a few cycles of this until the Sept. difficulty adjustment in BTC.
However, it won't persist for long as BCH bleeds lower and becomes marginal at best for anyone to mine on.