Hi Nick, welcome to the forum.
Looks like powdery mildew. Remove the most distressed foliage. The leaves with a complete or almost complete coating. Snip the stems back to the base.
Prepare a very mild solution of original Dawn dishwashing liquid and water. 1 - 2 tbsps. Dawn to 1 gallon of water. Have a container of clean water available to rinse your towel in. Gently wipe ALL surfaces of your plant with the Dawn solution. Rinse your towel between each swipe. Refresh your rinse water frequently. You do not want to re-distribute the mildew to the plant.
Pot up you plant to a larger, well drained pot. Remove as much of the old soil as possible. You can gently rinse the old soil off of the roots without harming the plant. As you rinse the old soil off of the roots rinse the entire plant (after it has been cleaned) .
New pot, fresh soil, clean plant.
Elizabeth - or Your Majesty
Living and growing in Lafayette, La.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown