I have two plants of the same strain, the issue is...

Hey, so, if you have them in such low light. Or if that's dark idk.. You need to stick to a set 18-6. It only takes a few days of a late vegging plant to do this. This isn't what's supposed to happen. Yes, a vegging pheno will show sex. But, to get like that. It takes a lot of not turning your lights on at the same time every day (you do have 24hr on/off simple adaptor right) Anyways. I suggest you actually make sure when they go into dark its fully dark..and with lights on. Make sure they aren't been shadowed. A way you can kick start them quicker back into veg & growing bigger. You need to use bigger pots. They're very small. So it's a factor of a few things stated above.. uppot to a new bigger pot. And make sure they get 18hrs of good light (that comes on at the same time on/off) everyday at the same time.

Its a normal phenomen called preflower and will show on every plant after some weeks of veg.

plants can display sex before being flipped to flower, it just means they are ready and mature. Think of it like plant puberty. They hit the point they can reproduce but are not in bloom yet. This is common. Seeds also do not act like twins and slight variations between them, called phneotypes. there is also the chance the pollen in one seed was from a different plant. No information where the seeds came from so bit of a guessing game.