Answer: Sunpatiens were bred for extreme heat and full sunshine; in trials at Georgia State University, they performed remarkably well during adverse weather conditions. So, I don't think your heat wave affected the plants. The problem is more likely related to watering practices or soil. I'd leave the puny plants alone - they may recover. If not, and if you decide to plant again, be sure to amend the soil with organic matter so it will drain well and after planting, mulch over the bare soil with additional organic matter. This mulch will help moderate soil temperatures, help slow water evaporation and also suppress weeds.
Best wishes with your Sunpatiens!
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