Well, it looks like shark did too good a job convincing other suckers investors to start masternodes, so it became harder for them to generate rewards.
Good news for MN owners, the Ionomy LTD is shutting down the MNs that were being used to support the 12 month XPY Stakers The "harder to generate reward" is due to current decrease in the ION block reward (as per schedule of the white paper).
I expect the number of MNs to increase as the coin migrates from staker to Masternodes...