The drop is probably down to a delayed 2nd announcement or the remnants of XPY people cashing in their ION from the 8 to 1 conversion or someone deciding to sell off a couple of masternodes or a bit of all the given reasons.
A peek at a 3 month chart should reveal to you that actually it looks like it's been in a longer term downtrend since roughly late March, which is probably when what little excitement there was around 'Crypto Gravity' finally died off. The increase in BTC-$ value has probably papered over this to an extent, but the truth is right there in the charts.