Q.What Is Wrong With These Two Small Plants?
Maybe due to the heat (41 degrees Celcius)?

Certified GKH Gardening Expert
This appears to be overwatering damage. Compensation for heat should be done with shade. Watering should, only, be done when the top 2 or 3 inches of soil are completely dry.
Soils that remain saturated without a period to dry out will suffocate plant roots. Be sure to allow for a dry period, and move the plants to shade during hotter portions of the day. You may need a fungicide to take care of any infections that can arise from wet soils.
Here is an article that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm