Answer: Sorry we cannot accept attachments in this forum so photos are out, but what you describe is fairly common with impatiens. Unfortunately they are prone to crown rot and it causes sudden wilting, just as you describe. Be careful with your watering, try to keep the water on the soil, not on the leaves or crown of the plant, and be sure to let the top of the soil dry out slightly between waterings. I'd trim off the affected plant parts. Let's hope for the best with your plant.
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