I'd like to see pictures of the juveniles. All will appear female until they suddenly don't. Egg spots are not a good way to determine a young betta's gender. It's a combination of egg spots, fins, body shape, yellow ovaries, and a beard that really shows who is what. For female, looks for the yellow patch within the body, showing where the ovaries are. They will also look plump and have very prominent egg spots even at a young age.
Males will be more stream-line, have a hint of a beard, their heads are larger in comparison to their body and fins more extravagant. Young males can and often do have false egg spots. They become more prominent if they were just fed.
How old are they and how many in each spawn? Are they from the same parents? There have been studies that suggest the more spawns the parents have the fewer males produced. Can't find out where I read that, it was a while ago.