Is there a reason why this guys plant looks so small compared to my 3 week old plant? Different strain? Because I'm growing hydroponically?

Dont mean to hijack your thread, just curious.
sum1cull911 Reviewed by sum1cull911 on . 3 weeks :) well guys this is my 3 week old plant i just want an others opinions on it ..i think it may be a female but not sure???:rasta: Rating: 5