If they were 4 to 6 months old in July, that would make them 6 to 8 months old now. Judging by their size in comparison to the dime in the picture, how confident are you that they are that old? They seem a little small.
With auratus, sexes are not often apparent until about a year old, sometimes even longer. I could not readily visibly sex my Costa Rican Auratus until they were about 18 months old.
Once fully mature the sexes shouldn't be too difficult to distinguish. Mature females are much more plump and larger than males. I would say in my auratus group the males are 2/3 the size of the females.
Prior to hurricane Katrina I had a tortoise rescue. I had Red Foots, Sulcata, Russians, Golden Greeks, Hinge backs, Malasians and box turtles. After Katrina my husband and I moved to TN and I had to re home all of the torts. My husband died in Sept of 2010 and I moved back to Louisiana. I don't have any torts now. I decided I would try PDF's. I always wanted them but DH would not let me have fruit flies.