Your plant is showing signs of a Potassium Deficiency. With a potassium deficiency, you’ll generally see symptoms on older leaves, but not always. Sometimes you’ll see the symptoms at the top of the plant. Leaves with a potassium deficiency get yellow, brown, or burnt edges and tips. The burnt edges may look a little like nutrient burn, except the affected leaves also start turning yellow in the margins. Give her a flush with clean, pH’d water that contains nutrients. Old damaged growth will likely not recover. Watch the plant over the next few days to make sure that the problem stops spreading to new growth.