Their bodies learn over time to adapt to huge temp swings. We see 30 to 40 degree differences from day and night every day of the year. As yours grow, they will get used to it. Definitely offer heat at night until you find they don't need it anymore. They should be fine during the day without heat.Thank you. My only worry is going from 65 to 30. I would think they are feathered enough to not be overly shocked and will simply love all the room!