Welcome to ATP Dom!!
Browning leaves can be caused by a number of things such as too much water (tap water contains chlorine and that too can cause browning on many plants), too little humidity, too much fertilizer and too much sun. They prefer to be on the dry side with bright indirect sun. Direct sun can literally sunburn the leaves. If it's only one leaf don't worry about it. If others are starting to go brown then see if you can change their environment.
It would help to know where you live and the environmental conditions your plant is living in - As in sitting next to an east facing window or heat register.
