I dont drop temps really at all. Maybe a few degrees but the snake room is kept so warm & humid that all i need to do is turn my house heat down a couple degrees. The temps naturally fall at night. The barometric pressure naturally drops. I just spray them more often to simulate the rainy season and I have 3 females now that are so swollen they look like they swallowed a baloon. (ovulating)

So the temp drop is not completely needed. Its whatever works for each person. Try removing the water bowl for a few days and spraying them down the next time you put them together..

Some snakes are just naturally late season breeders. You may need to seperate them for awhile and try again in a month or 2.