I don't think 68 is unreasonable at night. It is still cold at night here, with early morning temps in the 40's. The wild collareds around here have been out for about a month now. I do have a reptile heat pad under the sand that keeps my tank at 70 degrees during the night. It is controlled by a thermostat. This is a very thin sheet of plastic, thicker pads are made to go underneath the tank itself. Head pads are not recommended, but my house gets very cold at night in the winter. I work nights and heat with wood, so I felt I had to give them something.
I have 4 in the same terrarium and have mealworms out all the time for them. They love the mealworms and eat about 800 a month. If a mealworms turns into a beetle, they eat that, too. Plus I give them 8 or so crickets a day. (Yes, they are all fat!!!) Mealworms are not the worm of choice because their skins are hard to digest. Eve will tell you to feed them superworms instead, but they freak me out! Wax worms and silk worms have a higher fat content than the mealies or supers, good for when you need to fatten her up. (Mine don't get any of those, hahaha.)
This is a picture of 6 month old Hermes, aka Jabba the Hut, before I gave him away a few months ago. The others have not gotten this fat, and he has slimmed down some in his new home.

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Valerie
We may have all come on different ships, but we're in the same boat now.
--Martin Luther King, Jr.--
God bless the USA
vrk.photosite.com