Hmmm...
Black plastic ground cover... And soaker hoses under.
I'd take up the plastic.
It does sound like over watering... I've seen people drown their gardens in the drought...
Unfortunately, you didn't tell us anything about the soil... clay? Sand?
Or just how much water you were running out on the ground.
When I gardened in that part of the country, I got by fine on the water that fell out of the sky.
But maybe things are different now in Illinois...
I think I would replant... Maybe in a different spot.
