My dad rents out a student flat and as he is too unwell to manage it I do so via power of attorney . Two of the rooms have re current condensation problems around the windows. I have asked tenants not to dry clothes in their rooms and to wipe windows down ( can t be sure they have done so). Now it has escalated to outright mould around windows and in a clothes cupboard. What should I do? Get it checked out by damp expert? Just clean off affected areas? Is it worth investing in aa dehumidifier? Thanks for any advice.