Cannabis grows, flowers, and dies based on season.
It determines season based on day length.
Summer days are longer and summer nights are shorter than 12 hours.
Days start getting shorter after June 21st.
When you grow a plant at 12/12 from seed, you are stressing it into thinking 'oh shit it's fall already, and I missed my opportunity to breed'... what happens to a stressed cannabis plant that is trying to make seeds before it dies?
You all know the answer to this one.