How big is the "big one" I was under the impression that they are 2". The last to photos you posted are no help, the fin is obstructing the veiw of the gill. Try to post pics of both your JDs with the same pose as the FM in your avatar.
that looks like two males actually
but for the new pic the fishis fin is in the way of the gill but it kind of looks like a beat up female
also if you wan't to breed them and have something to do with the fry the go for it by a male if you do look for these things on a male
when small around 3-6'' look for
little color to some spots on gill plate
bigger mouths
high spangle count ( the shiny spots on them ) they will have rows going down there body from an early age
also the tend to be bigger around and have more red in there fins
also they will breed as early as 3-4'' i've seen a 4'' female breed with a 8'' male but never the other way around males tend to need to be 5-6'' before the start to notice girls
from what i can tell they both look like females due to the color on the face and lack of color on the body. this is a pic of my male. the blue stops right at the "jaw" line. where the females have a lot of blue all over the underside of thier face. i will post a pic of her if i can get her to stop hiding all day long.