I have heard and even seen in a couple of my animals that having a change in environment can throw them off their game. It is possible that their are things in the house that are a bigg enough difference that your snakes feel like their environment has completely changed. Then again they may just be taking a year of.

How many of the females you are breeding this year bred last year..they may not even go this season..then again they may just be going later to to average rain fall being lower than this time last year.. there are thousands of reasons they might not be breeding.