If you haven't put it in 12/12 and that isn't an autoflowering strain, what you think is females probably hasn't shown sex yet. Real hard for a newb to 'read' preflowers. Vegging for a long time is fine by me. Depends what you're going for. Training? Do you have more space than you have plants to fill it? Are you going for a SCROG approach? All good reasons to veg for a long time. OR... Are your plants going to outgrow their space when they double in size during flower? Then put in 12/12 NOW!!!
Yellow low leaves commony mean 1 of 2 things: 1, they aren't getting much light therefore the plant doesn't need them any more. 2, you're low on nitrogen and the plnat is sucking it out of the old growth. If you;re already under HID lights, you can bend them and get more light to low growth to keep this from getting worse if it's a light problem.
I'm going to say, you've already got 4' monsters, bend those suckers right over and put them in 12/12 before they turn into trees.