Check the underside of the leaves for damage or spots. Look for dried plant parts such as dried stems and yellow, reddish or brown leaves. If you are doubtful about a certain plant, don't buy it. Buy only healthy plants from a reputable and established seller. Ask if the plants have been treated with pesticides.
Some house plants are very particular about soil and fertilizer.
Your plant may need to be repotted. You will need information regarding soil mixture. While you are in the plant store you might as well purchase a new pot and drainage saucer, the proper soil mix and fertilizer.