If you water your ferns and a majority or the water runs out of the sides/top, it means that water is not getting to roots like it should and your plant will soon start to show signs of deterioration. When the water runs over the top and sides, it means the plant is likely root bound or there is too much debris on the surface of the soil for the water to get through. Try cleaning out the brown fronds, birds nest, and loose debris sitting on the soil surface. If this does not help, then it is time to replant in a larger pot or divide the fern.