Pepper seedlings close up near night?

[gardeningman 101]

I'm new to vegetable gardening indoors. I decided to attempt to grow some jalepeno peppers indoors under a 2600lumens florescent. They're a few days old, still have their first fake set of leaves. They are lit about 1ft. away from 6am to 10pm (16 hours). The question I have is, around 7pm and on, they seem to 'close' up, both leaves come together partly. Is this normal? A friend told me that's pretty normal. Is this becuase of the 16 hours, but it's really used to the 12 hours a day from the sun, which is why they close up around then. Should I keep them on 16 hours? and they'll get used to it? Should I just change it from 5am - 9am or something like that?