Inappropriate watering is the number one cause of a browning Anthurium plant. If overdone, it can lead to fungal and bacterial invasions and make your plant sick. If you see this happening, immediately check the roots of your plant. If there is visible browning or blackening down there, confirm an infection, and take appropriate measures. Isolate the plant, prune its diseases or dead parts and repot it if needed. Spray a commercial fungicide and take care of it as you normally would.