Firestarter/WMG

The Pineal and Pituitary Glands used to Synthesize Lot 6 Came from Carrie White.
Basically, The Shop caught wind of the Massacre at Prom Night. They knew that the result of it was through psychic interference. So they dug up Carrie's body and extracted the glands. Using them on rats at first, but then moving to human trials. While in the movies, Carrie only displayed Telekinesis, it was implied in the original novel that she's also Telepathic and Pyrokinetic among most abilities. So it stands to reason that Andy and Vickie inherited her telekinesis and telepathy through the experiment, while Charlie inherited her ESP and Pyrokinetic abilities.