Is this condensation

[Emmarose21]

Had a new roof and valley fitted about 4 weeks ago but I’m still having problems. There’s no actual leak but grey cloudy quite damp patches. There is a very small space above the plasterboard with joists attached to the ceiling. Just wondering is it condensation? Would an air vent in the ceiling help? Marks have been there for 2 weeks they are colourless, not yellow or brown. There is a chimney above which the roofers have resealed and leaded..
Any help would be greatly appreciate.