mine are going like that a bit, I take off the affected leaves but I think its the cold and damp,

It's powdery mildew, a common fungus disease when the nights are cool and damp. Try spraying it with a mixture of 2 ml baking soda and 4 ml of organic washing up liquid in a liter of water. Potassium bicarbonate is even better than baking soda, but may be harder to find.