Is there an antidote for weed killer?

I just found out that the woman who use to live on my property used chemical weed killer on the soil and now nothing grows to completion. Is there a way to flush the soil to stimulate growth? She claimed she used a very diluted form of the weed killer but once my vegetables root past the 75K (kilos) of top soil I added things dry up and die. From what I read the soil may not be usable for up to 5 years...