It's likely that what you are seeing is your liver doing its best to keep your BG at the levels it's been at recently. Your liver will have accepted the previous high BGs as "normal" and will be trying to get you back where it thinks you should be, by making new glucose and adding it to your system.
Livers are slow learners, and it could take a while before it gets used to your lower levels as a new normal. I think it took mine about four months to completely get used to it - and left to itself when I fasted, my BG went up.