It has been suggested that the male:female ratio can be affected by several factors, including nutrients and temperature in the period leading up to and around when they first show their sex. You'll probably need to search around for the details of the theory, they are out there somewhere. Personally I am inclined to believe this.
On the other hand, it is still just a game of chance whether any given individual is going to be a male or a female. In small batches of seeds it is perfectly possible to have a high proportion of males:females, and it may be that all of the factors that might change this don't do that much to change the ratio. I reckon this time you were probably just unlucky, but it does reinforce the fact that if you are looking for a certain minimum number of females you need to start out with quite a few regular seeds to ensure you reach your target. Most times you'd probably end up binning several perfectly good females because there wouldn't be room to grow them all.
Some you win, some you lose.
:Sharing One: