Thanks for the replies! Mole- yeah it is rather humid of late, but then it always is in the summer! Thankfully high pressure is taking over this weekend- so dry, sunny & warm at last!

The plants are grown outdoors on my patio. They do not come in at night as I ain't getting up at 4am to put them out when the sun comes up! I can see no bugs on them (well other than the odd fly the lands on them from time to time). The mould is confined to just the branch to stem joints. Leaves are fine. The green stem coating has been replaced with a dirty grey colour.
Soil moisture- I generally water them till they're soaked, then leave it till the soil becomes dry again. It has rained a fair bit here lately, but generally only light showers. I take the plants in during heavier rain.
Photos- I will be able to get some tomorrow which I shall post up on here.

keywestcathy- are these treatments likely to kill the mould to allow recovery, or simply stop the spread of mould?