Just a little added info as it can be important. If you weigh the bow with the hand held Cardoza scale it may show less weight than others. My experience has shown these things to be notoriously about 4-5 lbs light.

As the others have said, it's most likely string creep. As the string and cables creep it reduces the prestress on the limbs. Getting things back in spec usually helps.

Don't expect weakening of the limbs. Although it does happen, worst case scenerios show only a couple pounds of weight loss over maybe ten years or more.