There are dozens of diagnostic questions to ask before making a fertilizer recommendation.  Many of them have to do with soil type and structure, plant type, watering habits, and the symptoms of poor plant health that gave rise to the initial question.  And, often, the real problem isn't a lack of nutrition but something else altogether.  Inappropriate plant choice or siting, for example, or poor watering habits.  In those cases, the recommended remedy may not involve soil amendment or fertilization at all.

There is, in truth, only one correct, honest answer to the question...