Were the plants, especially potted plants subjected to a sudden drop of temperature such as being near a window on a cold night or a power outage? The plant may yellow some lower leaves and drop them to conserve energy for what appears to be a "crisis.
First things first....get the plant to a stable environment with a room temperature within the recommended range of the plant. Second, re-plant to a larger pot if additional temperature drops are expected in the future. The additional capacity of soil will help insulate the plant and reduce the amount of shock during the cool-down periods.
Plants generally recover quite easily from unexpected cold shocks. Give it a couple weeks to sprout additional leaves or to halt any yellowing that may remain present.