If they are not autoflowering strains, and they are grown from seed, not clone, then plants show PRE-FLOWERS around 6-8 weeks veg time (varies by strain I'm sure, but this is what I've seen). PRE-FLOWERS are indiciations that your plant is sexually mature and is ready for flowering. The balls are males, the hairs are female. Cut the balled plants and remove them from the garden unless you plan on breeding. Once the pre-flowers are showing you can easily identify what sex the plant is, and you can then change the light schedule to 12/12 and begin flowering as the plant has shown it is now mature enough to flower.
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