Identifying Male and female

I have 8 red comets and two blackmores.
The blackmores are too young to identify.
However the 8 comets are from 1.5 to 2 inches long.
I have now noticed since having them that they are changing in shape.
Would the female be getting larger around the girth than the males ?
I have three of them distinctly bigger around the girth.
As its coming into spring here....I have been awaiting any noticable
behaviour ...or changes in body.
ie the white spots for male.
Are the females bigger so to carry the eggs.?

NZed
PS Since they have the new tank they have really adjusted well. Testing the
water regularly. They are also very entertaining and curious.
We have them in the front of our shop...if a customer sits next to them they
come over to investigate.
I moved the air pump nozel in a different direction and they had great
fun...doing laps around the tank....swimming into the nozzel.