You can expect some gradual leaf loss as your Polycias acclimates to your home. It is usually the older leaves that die. As they die, they exhibit a variety of discolorations that you are seeing. Don't try to read into anything into the variations of the dying leaves. Give the plant a good shake to get the already dying leaves to fall so you can remove them all at once.
There are some things that can add to the leaf loss that you want to avoid, specifically inadequate light and letting the soil get too dry. Your plant is too far from the window. It must be within a meter of the south window to thrive. In reduced light, it cannot support as many leaves.
Make sure the soil stays moist. It looks like yours is potted in a terra cotta pot. If so, you will need to give it a thorough watering as soon as the surface of the soil feels almost dry or just slightly damp.
