Brown tips on plant leaves

Q: What is causing the tips of my plant leaves to turn brown and wither?

In this case, I will generalize because there is not enough information regarding things like growing conditions, type of plants, and other past history. Brown tips and withering leaves may be caused by numerous things, including uneven watering, inadequate humidity, fertilizer toxicity, aging of the leaves, nutrient imbalance, temperature, disease, and others.