Help with first grow

This is our first time growing with seeds. The first 16 days were on a 24 hour light cycle and then they were cut to 12-12 after 16 days. By day 29 one of them was already showing some buds. The other 2 are still not showing anything on day 36. One is really tall and skinny with few branches and the other is really bushy. What do we do to get them to show sex so we know if they need to be pulled or kept.
 
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