You should not have topped a plant that small dude that was the wrong thing to do. It did not have a chance to produce the axons needed for healthy long life and large buds.

Cropping has nothing to do with THC. THC is in the genetics and you can only grow the plant to its full potential and not beyond in terms of THC percentage.

You should not have stressed such a young plant your risk of your plant turning hermie now have increased by 10 fold.

Happy growing