Is this on exterior wall or remotely under a bathroom/kitchen in the house.? Does it leak when it rains or when somebody flushes a toilet? Runs dishwasher? Showers?

Delaminating paint/plaster/sheetrock is a sign that significant moisture is absorbed into its composition. And continually being exposed to it a steady pace. It’s may not be enough to precipitate out to significantly form a wet spot or puddle. Much like a leaking washer on a shower cartridge, a shifted tub shoe or an old copper/CI drain connection that has a slow leak on certain occasions. Either way, the only way to fix this issue is address the source of the leak first. Cut out a square in the ceiling twice the size of the damage. Leave it open to dry, and Liberally spray either dilute benzyl alcohol/water or dilute bleach/water. That will disinfect and aid in the evaporation of water. Replace with appropriate thickness sheet rock