Explain what is probably going wrong in the following scenario: Situation: Using a range of different fertilization techniques and products, a gardener has been working to improve fertility on a stretch of lawn that had very poor, sandy soil. The gardener has added a range of soil amendments, including additions of clay, compost, peat moss, and NPK fertilizers. For a period of time the gardener seemed to succeed, and he increased his treatments. Recently, though, discolored vegetation that seems almost drought-stricken has been appearing in the grass. The gardener is now wondering what has gone wrong.