Q.Plant Producing Flower But Not Going To Produce Healthy Fruit
In light environment about 16 -18 degrees regular feeding – watering when dry soil to touch

Certified GKH Gardening Expert
Unfortunately, this can be due to many factors, and to make things more complicated, it can depend on the type of plants in question. Mainly, when there is a lack of potassium and phosphorus in the soil, this can happen. But it can also happen if there is too much nitrogen, or the pH is not in balance. It can be due to specific fruiting conditions for specific plants, as well. Since I do not know the plants in question, what I could suggest is have your soil sampled by your local agriculture extension. They can give you an accurate reading of your soil, you can adjust accordingly.
This article will help you understand a soil test, and what they test for:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/plant-problems/environmental/plant-not-blooming.htm