I would need to see pictures of your plant to comment on your situation and what stage they are likely at.
However the first thing you need to do is forget the calendar! Plants don’t grow by a calendar. They don’t care when a breeder says they should be done and they won’t be done until they are finished. How long that is depends greatly on your grow environment, and the genetics of what you are growing.
Secondly cannabis follows the same growth cycle that many other plants do, here is a chart.
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After you switch your lights to 12/12 it takes time for the plants to begin flowering. This transition period commonly takes 1-3 weeks depending on all the variables. Then once the plant is hormonally ready it begins changing its growth to actually form flowers.
Cannabis flowers grow larger all through the flowering cycle. Then at the end the stigma(pistils) turn reddish and shrink towards the buds. Once about 90% have done that the plant is done trying to reproduce, and is entering the ripening and maturation stage.
During ripening the buds don’t appear to grow outwardly, but are swelling up inside. They are getting denser and are stacking resin. That ripening stage generally takes 2-3 weeks but can take longer. The weight and quality that is added during this period is significant, and you should learn to have the patients to wait out the plant.
I won’t hesitate to say that MOST new growers and many long time growers(90%+) harvest weeks early and don’t ever get the full potential of their plants.