The smaller ones may be your females! I've noticed males taking off sooner and looking stronger then gotta get cut anyway.in growing some kc mangoes, started off with 10 regular seeds, most of em didnt have space so they had to go.
now i have 3 mangoes and 2 afghan kush feminised under 250watt hps, and i must say the mangoes are not consistent in terms of genetics( though its my first time growing) as only 1 of the 3 seems to be healthy(what if it turns out to be a male? =( ) and the other 2 are noticeably smaller. the female AK's are doing fine too.