Help determining sex of plants

[Fragua]

Hi everyone,
I have three six-week old plants, and I need some help determining the sex.
I'm attaching 6 photos, two each, named A, B and C.
I can see some more evident sings on plant A, but not on B and C (as far as I know).
C came from a Sativa seed (San Francisco OG), and A and B are Indicas (but not sure which strain).
Could anyone give me some help me?
Many thanks in advance!

Juan

[Cloud]

To soon to tell. I've seen them resemble balls and later on they get pistils. Flip to flower and wait till you get some little hairs or more defined balls. Or keep in veg till you see hairs or balls

[Fragua]

Thank you so mucho for your comment! I was wondering when to flip to flower, and it seems like now its a good time. Deeply appreciated!

[grouchyoldman]

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Alas, too soon to tell, but I'm gonna guess Fem for "C" at this point.

Here's an idea I read elsewhere but I haven't had a chance to try it yet. Put them under 12/12 lighting for two full Day/Night cycles then go back to your veg lighting. The claim is that this will trick them into an early show. But they'll stay in veg after switching back.

Interesting and I don't believe that it would hurt the plants long term. If you try it, please post your results!

Cheers,

-Grouchy

[Fragua]

Thank you very much for your comment Grouchy! I guess too that C is Fem. The idea sounds interesting. I will think about it. Cheers!