I haven't been able to find much information on if the nighttime temperature should be different for smaller dragons. I saw on one website that it's better to keep the tank up near 80-85 at night but haven't been able to cross-reference that with anything. Since then, I've kept the tank up and have been concerned about the tank dropping into the 70s for my 2 1/2 mo. old. Am I overly concerned?
70s is fine overnight. I like to keep my tank between about 70-73 (using a programmable thermostat and heat projector). A bit of a cooldown is natural for both young dragons and older ones. I'd imagine keeping a young dragon a little warmer won't do harm but I never had any problem keeping my dragon at room temp overnight (high 60s low 70s) when he was little. He just curled up in his hide and was content.