Bottom Leaves Drooping

I have a couple of plants that that I started a few months back, my very first attempt with seeds from a bud I bought and scavenged. They are in a room with flouresent tube lighting and a small fan blowing on them. Up until recently they were doing fine. I transplanted them into a gallon size pot cause they were about a foot and a half tall. I also switched the light cycle from 18/6 to 12/12. Since then the very bottom leaves have been first drooping then falling off after a few days. There is no color change, they stay perfectly green until they shrivel up and fall off. The top leaves are doing just fine. Is this normal? Any advice would be appreciated. Thanks. I can post pic's if you think that would help with a diagnosis.

Did you get better lighting for the flowering stage? he floros will work for clones and maybe the veg stage if kept small but you need much more light to flower especially since they get less light time they need more light when its on.Not enough light could be killing them.

If it is still in the veg stage, just leave the lights on all the time, only switch them down to 12/12 when ur in teh flowering stage, unless thats wut stage your in rate now