The only thing we can say for certain is that your plant is stressed. Just like us, their stress can stem from different areas of care and environment. Unlike us, they can't talk, so it's up to you to figure out what's bothering them.
How widespread is the yellowing? If it’s just the bottom leaves, see the answer in the next question about leaf drop.
One of the most common causes of yellowing leaves is inefficient watering. Finger your soil a few inches deep. Is it very wet? If so, you may be over watering your plant. Is it bone dry? It may be time for a drink.
Is the plant near a drafty window, in front of an A/C, or near a heating unit? Large swings in temperature throughout the day can stress a plant out.
Still unsure? Text us some pictures at (646)430-8699. We up.