The purpose of plant leaves is to use sunlight and convert it to energy for the plant, not absorb fertilizer. Roots on the other hand, are capable of taking up nutrients and translocating them throughout the plant. It's true that foliar feeding can sometimes quickly green up yellow plants. Amazing results are often seen when a soluble fertilizer containing iron is sprayed on plants that are deficient in that mineral. Though recovery might be rapid, it is usually temporary.
Some soluble fertilizers have two different mixing rates, depending upon the application method.
A much weaker solution is used for foliar feeding because there is more danger of leaf burn when compared to concentrations used for soil application. I am growing pepper plants indoors and they are blooming, but the flowers produce no fruit. Move them to an area outdoors that receives full sunlight. Peppers have several requirements that won't be satisfied inside of a house. In addition to the lack of sufficient natural light, peppers are air pollinated.