Instead of looking for diseases, check for insects and mites, which commonly infest indoor plants. Environmental or cultural conditions are probably to blame. Following are some conditions that can cause problems, the symptoms they cause and ways to bring the plants back to health. Humidity in houses is generally fairly low, and it decreases further during winter when the heat is on. Many foliage plants perform best under high humidity levels, so low humidity can cause leaf tips to dry out and turn brown.
Inadequate water is another common problem with indoor plants.
When the soil dries out, plants wilt and leaf margins may turn brown. Yellowing and dropping of leaves are other symptoms of inadequate water. To help plants with these symptoms, water them thoroughly when the top half-inch of soil is dry. Keep in mind that symptoms of overwatering are similar to those caused by inadequate water, because roots in waterlogged soil function poorly. So if your plant is yellowing or wilting, or if the leaf edges have turned brown, check the soil moisture level before assuming that it is dry.