I have 7 altogether, but 3 of them I know are definitely male (they have big bristles that branch off into 2).
Here are the ones that I'd like to know the sex of:
I think this one is a female, as it is the roundest of them all. It is about 2 - 2.5":

Here are 2 next to each other. They are bout the same size as the first one. I think the top one is male as it has a red dot on its head, but I'm not sure about the bottom one:

And this is the last one (with one of the bigger males in front:

Also, does this one look very healthy? It is one of the definite males:

cheers,
Ben