Since youre using cfl at 8 in distance that's pretty good, have you put your hand at plant level and see if it gets too hot after 15-30 seconds? If so the light needs moved. You say you reduced lamp distance...did the curl happen before or after that change? If none of this applies I'd say look into your watering ways, overwater can do a curl at this early stages. If it curled under I'd say the nutrients. Try looking into those various things, light, heat, and watering. Do each thing 1 at a time so you'll know the culprit. Best of luck, the plants at least look very green and healthy, slight curl included.
Oh ps. Being in a space bucket, you'll want to be checking the heat and humidity fairly often. Those small areas tend to be affected more by temp/ humidity due to the confined space.
