I think pictures and soil test would be a good start.

I would not have tilled it in, but what's done is done.

Scatter some whole ground corn meal over the soil at a rate of 20 pounds per 1,000 square feet. Moisten that and give it 3 full weeks to work. You might also spray the area with a milk and water solution (50/50 of any kind of milk including spoiled, skim, strawberry flavored, goats', dehydrated, or anything else). Several years ago I revived a colony of nearly dead African violets using nothing but milk and water. It works surprisingly well against fungal disease, as does the corn meal.