Sounds like you are just like the rest of us, you wanna get those little fuckers to flower as quickly as possible. I have found the growing process is very good for teaching patience and is very Zen-like if you let it be.
So you want about an ounce per plant, that is definitely doable with 3 plants under a 400 watt lamp. I would flip them to veg when they are around 12 inches high, that will give you approximately 3 foot plants when you are ready for harvest. General rule of thumb is 2/3 growth after flipping to flower, but that can vary according to strain.
As for your area not being 100% light proof, this is very, very important when you flip to flowering. You will want to make sure can you get it as light proof as you can, because any light during the dark periods will fuck things up.
I see your plants seem to be curling or 'tacoing', how close is your light to the plants? Also, they seem to be a little plastic looking, what type and how strong of nutrients are you using? Either way they are looking decent so don't get discouraged or frustrated, we all have issues to deal with when learning to grow. I think you will be hard pressed to find anyone that gets it completely right every time and doesn't ever have issues, that motherfucker is a liar!
Good luck and keep it green!