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It sounds like you have powdery mildew. This article will help:
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm

This article will help you: https://www.gardeningknowhow.com/edible/vegetables/eggplant/what-to-do-for-eggplant-blossoms-drying-out-and-falling-off.htm

Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/eggplant/eggplant-problems-eggplant-pests-and-diseases.htm

You can use it as a reference for the most common eggplant pests and disease and then perform a Google search for pictures of them.

You may have an issue with pollination or too much nitrogen fertilizer, which can result in many flowers but little to no fruit. Offsetting it with phosphorus may help with this. Here is additional information that may help: https://www.gardeningknowhow.com/edible/vegetables/eggplant/what-to-do-for-eggplant-blossoms-drying-out-and-falling-off.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm

This article should help: https://www.gardeningknowhow.com/edible/vegetables/eggplant/what-to-do-for-eggplant-blossoms-drying-out-and-falling-off.htm

Plant collars are simply a form of protective barrier placed around the stem of plants. Some types may even go around the plant's base. They are available through most garden retailers. Many people will also make their own from plastic container lids (to go around base) or toilet paper/paper towel tubes (to go around stem).