Check conditions around the leaves
The room's temperature display does not necessarily describe conditions immediately above a radiator. A plant on the sill may experience a different local environment. Assess the position with the heating operating, not only on a mild day. Leaves should neither rest against hot surfaces nor sit in an unsuitable stream of warm air.
Suitable conditions depend on the species. Check its temperature and light needs. A bright position is not appropriate merely because the plant looks decorative there. If the combination of warmth and location does not work, change the position rather than trying to compensate with continually increasing amounts of water.
Plan a useful small move
Consider beside the window or farther from the radiator where enough light remains for the species. Do not simply move the plant into the darkest corner to avoid heat. The conditions need to work together. Observe the alternative at different times of day before assuming it solves the problem.
Also consider cold air during ventilation and the space behind closed curtains. A pot may be warm by day and end up in a cooler window gap at night. Keep leaves away from the closing window and allow easy handling if the plant needs temporary movement while the room is aired.
Avoid jumping to a diagnosis
Brown leaf edges or dry patches can have several causes. Check the position, moisture and container together. Watering more on suspicion can create another problem where the medium is already wet. Observing the actual pot matters more than following a general winter rule.
Do not obstruct the radiator with a dense barrier of plants. Its intended heat release and controls must remain usable. One suitable plant in an appropriate position makes more sense than a row of sensitive plants directly above it. If no location meets the requirements, another species may suit the room better. The arrangement should respond to living plants, not only to the empty area on the windowsill.
