I did the same thing with some bag seed a friend gave me. As they grew I filled the cup in more. That's a good looking plant, I'm curious about using a light leak to produce seeds. Care to elaborate? I'm in a position where I have one mother and what I got is what I got type deal. I'd love to mess around with stressing to make seeds. I know the strain I have will do it because it had done it before unintentionally. Last grow I did ended up with 10 seeds 5 worked and I'm growing them now.
During 12/12 a light leak can cause a plant to stress enough to cause it to make seeds. Technically it will be a "hermie" but in the 4 years I grew the only hermie I ever got came from a seed bank (tude freebies)
The female will try to "survive" (keep the strain alive) when it's stressed enough and create seeds. It's not always a light leak but it can be enough to stress a female plant to make seeds in order to try to survive.
You can also sex a plant and put it back under 24/24 to revert it to a veg state, that would create a lot of stress and if you flip it back into 12/12 it will potentially "hermie" and create seeds, but the seeds, at least in my experience and from what I've read, usually tend to be female.
"Female" seeds are not natural in nature, its man made, so there is always the potential that a "fem" seed will hermie.