My snake tank gets a little colder than that at night and my female eats fine and is a good weight so no I do not think so. As long as you have a warm hide they can go into when they get too cold I think that it should be fine but if it drops below 75 F I would put a towel over the front of the tank at night so it insulates a little bit more. As long as your snakes are healthy and eating it shouldn't hurt. Please correct me if I am wrong I am just going off of my own experiences.