With out sufficient light plants your plants will slowly die of starvation. With out enough light the soil stays sopping wet after waterings and allows bacteria to grow and attack your plant.
In the winter we have far less sunny days and even when the days are sunny, the sun is lower in the sky and not out as long as needed by many plants.
In the winter supply your plants with extra light. A table lamp with a fluorescent bulb works wonders and costs next to nothing to run. Set one up on your desk or a table and rotate your plants under it if there are too many to fit. It doesn’t take much to save those plants from starvation.
If the windows are not too cold for your plants move them closer. If possible, move them to brighter windows for the winter. Plants that sit in in west and east windows can be moved to southern exposures during the winter. Those normally in north facing windows can be placed in east or west facing windows. If you can move back a curtain with out exposing your plant to too much cold, that helps too.
Don’t starve your plants this winter, supplement their diet with extra light.