Each year a portion of the interior needles on evergreen trees will cease to grow and this is normal. In a stressful year, more needles may turn brown as the evergreen attempts to balance the needle load with available soil moisture. Without some outside force causing the needles to fall to the ground, they will remain in the canopy. Interior needles will not recover as this is a natural occurrence. Watering will certainly aid in the evergreens overall health and could limit needle loss in the future. you could also contact your local Extension Service to see of t here are additional conditions impacting your evergreens.