It is normal for plants too use/drink/take up less water near the end of flowering. They are nearing the end of their lives and to make sure they perform their function to the fullest, producing as many viable seeds as possible, the plants basically cannibalize themselves using up all the processed stores nutrients in the plant and drawing it in moisture taken from the plant matter to achieve its main function that of course is carried out in the buds.
Of course it cannot do that, making viable seeds since you did not pollinate your females, I hope, but the plants do not know that so they go about their normal functions.