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There could be a few issues that cause blossom drop!

https://www.gardeningknowhow.com/edible/vegetables/pepper/pepper-blossoms-falling-off.htm

It looks like damage from the aphids. This will recover with time. I would keep dolomitic lime handy, as this is very helpful for a recovering plant.

Can you include a photo, your USDA zone, and what conditions the plant is experiencing? This could be many things, and I will need more information to make an accurate judgment.

Can you include a photo? I'd like to give you the best advice but this could be many different things. A photo will help me to see what is going on, exactly.

Mature plants that are fruiting will require something that is high in phosphorus, with an intermediate potassium amount, and low nitrogen.

"Bloom Boosters", as they are called, will contain just those proper ratios. You will want to apply these at 1/2 or 1/4 strength to start out. This is to ensure that the plants respond well to the nutrients.

This article will help you to grow Jalapenos: https://www.gardeningknowhow.com/edible/vegetables/pepper/growing-jalapeno-peppers.htm

t could be in the genetics or a cross pollination has occured, or a factor in the growing conditions. Here is an article with some points to consider:

https://www.gardeningknowhow.com/edible/vegetables/pepper/no-heat-in-jalapenos.htm