Question: My plants have brown edges around their leaves. It starts at the tips of the leaves and works its way completely to the bottoms of the leaves. Is that a disease?
Answer: Diseases and insects will always be random in their effects. Anytime you see marginal or tip burn of leaves, you have to know that moisture stress is related somehow. If you think about the human circulatory system, it can help explain what has happened to your plants. Those edges and tips are the points farthest from the roots, so they’re where the plant will dry out first and will get water last. Either you have let the plants get far too dry at least once, or they have suffered root damage. You may have over-fertilized them, or they may have some type of stem damage that inhibits their uptake of water. That kind of burn can be caused by sudden hot and dry winds (not protecting a plant on its way home from the nursery, as example), also by taking a plant that has become accustomed to moist, shady conditions and putting it into a hot, sunny location. Whatever the exact cause, it’s related to the plant’s inability to get water clear out to the tips of its leaves.