I have 3 plants 2 are already confirmed female, the other 1 was planted about a week before both of my ladies and it is showing no signs of sex and it is almost double in size of both, anything I can do to force it?
Males are frequently taller than females. It's probably a male and just taking longer to show than the females. Extra Potassium speeds up the preflowering process.
Males usually show sex first. Is it Sativa? Sativa strains are taller and take a while longer to show sex than the shorter indica. Give it time. You can always cover it for 12 hours a night with a rubbermaid garbage can or something big enough to fit over it and block out light. But make sure you don't leave the lid on when the sun hits directly on it or you will cook your plant.