Failing mortar will show more on your chimney breast walls. This is from your chimney top. Open pots cracked flaunching and no working fires to help dry them out will dampen your chimney breast walls and sometimes slightly spread onto your ceilings. It’s hard sometimes for homeowners to distinguish the 2 separate issues failing lead or mortar, but a tip is that a lead problem won’t dampen the chimney breast wall in your bedroom, so if water marking shows on your ceiling just touch your chimney breast and see if that feels damp.
