I can't see your picture but Yes overwatering can cause yellowing. I found this online: Overwatering or underwatering are the most common culprits when a plant's leaves turn yellow. With potted plants, it is crucial that you only water as much as the plant needs. If you have a plant with yellow leaves, check the soil in the pot. Is it dry? Is it soaked? If plants don't receive enough water, they drop leaves to prevent transpiration (essentially, a plant's way of sweating) to conserve water. Before they drop, though, the leaves will typically turn yellow. If the soil is dry and this is happening, make it a point to get the plant on a regular watering schedule. Too much water can be just as damaging to leaves. When the soil doesn't drain well, an overdose of water leaves the soil waterlogged and root systems can literally drown. Without oxygen, roots start to die.
Other reasons mentioned: Natural aging of plant, cold draft, nutrient deficiency.
So if you don't think it's just from age, start with the water situation and see if it helps. Hope you figure it out.