Avoid overwatering and overfertilization. Our tendency is to water plants on a regular schedule, such as once a week. Slower plant growth means less water and fertilizer are used by the roots. When soil stays too wet, oxygen is more limited for the roots, which limits root growth. Check to make sure the soil is dry on top before watering.
It does sound like the plants with older leaves turning yellow and falling off may need additional fertilizer. When plants do not have adequate nitrogen to support new growth, they transfer it from older leaves to new growth.
If you use soluble or liquid fertilizer, apply it at half the recommended rate. I like timed-release fertilizers like Osmocote. Their release is directly related to the water that is applied. The granules are covered with a porous material that allows water to seep in and dissolve a little fertilizer and then seep out. So the plants receive a little fertilizer every time they are watered.
You may want to consider adding or replacing some of your plants with those that need less light. Go online and search for “low light indoor plants.” Some of my favorites are cast-iron plant (Aspidistra), peace lily (Spathiphyllum), Chinese evergreen (Aglaonema) and snake plant (Sanseveria). Dracaena, dieffenbachia, parlor palm (Chamaedorea elegans) and devil’s ivy (pothos) are also tolerant of low light.