Kind of tough to tell but he last picture shows some bulges running up the sides of the tail. Females tend to be really lean up the sides, with the noticeable bugle in the middle. Sometimes you can move the tail side to side when its bent back and the slight pressure can reveal the hemi penal bulges a little more. Some males just have small errr... you know.
With some dragons is is difficult to tell until you can hold it an manipulate it in your own hands.
Jeff