Changing the Light Schedule

My plants are currently gathering light during the day while I'm at work (and some hours before and after).

However, I want to switch them to getting light at nighttime, since the rates of electricity go down a good bit.

Can I just randomly change it over, or should I do it gradually, or not at all?

You can change the cycle, and it should not effect it. One change and the plant will get over it.
How long have you been vegetating your plant, and how many growth nodes ( sets of true leaves)?

It's day 9. They each have two sets of true leaves. Both right at the top.

I had the lights too far away, so they were stretching. But now the lights are about an inch and a half away, so I'm waiting for them to thicken up and grow some more nodes.

I don't have a camera (broke mine), so I'll take my moms next time I stop over her house so I can get some pictures up.

It's my first grow, so I'm not expecting much. =)

Do the change, but leaving the lights off for one day when you would normally have them on and then turn them on that night instead. That will start you on the new schedule you want to start. Your plant/s should recover fast, if they have to at all.

Awesome, sounds good to me. Figured I'd try and save some electricity.