I had a neglected patch (10 x 4 ft) in a corner of my garden infested with grass and dandelions. Four weeks ago, I sprayed them with Roundup. A couple of days later, I also poured a gallon of pickling vinegar on the weeds. They died soon after. I watered the area every week and it rained a couple of times as well. A few days ago, I planted eggplant there and it quickly wilted, the lower leaves became scorched brown and the new leaves are pale yellowish-green. I tested the soil with a pH kit and I got 5.0.

So my question is, is the damage due to residual glyphosate, residual acidity, or something else? Was a gallon of vinegar too much?