I have a slowly worsening leak on the top room in my house. The house was built in 2003 with a study in roof space of the house. Several years ago a faint mark appeared on the inside slope of the roof(highlighted blue). A year or so later, marks appeared above the 2 windows and then more recently significant shadow marks appeared near the chimney (highlighted red). This has spread and damp readings show figures of between 15% and 23%. I have called out some roofing guys and they have taken a look and applied some sealant in a few places but this has not helped at all. I have used a drone to take further pictures as attached but these don't really seem to show a clear cause. There does seem to be some faint cracks on the chimney and a few marks but I'm not convinced these would explain marks of this extent. Any suggestions of what to do next or possible causes would be very gratefully appreciated.