-- Pest or disease issues.
               -- Natural causes such as acclimatization or age.
The first step in solving the problem is to determine where on the plant leaf the problem is occurring. Is it along the edges or on the tip of the leaf? Are there brown spots?
Brown leaf tips
When the tips of the leaves appear dried out, thin like paper and crumbly, that's a good indication that you have a water or fertilizer issue going on.
Most houseplants take water up through the roots until it reaches the leaves, where it nourishes the plant through photosynthesis. If there isn't enough water to go around, the leaf tips turn brown because they are the last in line.