I also think it looks like powdery mildew.
The 'good news' is that you've caught it early, and if you get to sort that out now, it's hopefully not going to be an issue.
I've used milk and chilli with good results. My mate also had the same problem, so I told her about the spicy milk, and after one session of spraying, she sorted that out, and it never came back.
- Fresh milk
- Dilute with boiled but cooled water to 10-20% milk:water
- Chop in some fresh chilli or a few drops of Tabasco
Put that into a spray bottle, and mist the leaves - both the top and undersides.
Not just the visibly infected leaves, yes do those few thoroughly, but give the whole plant (and any neighbour plants) a decent spray.
You will find that a lot of the milk runs down the leaves, and collects into drops on the leaf tips. All good.
If you keep it in the fridge, the mix will be good for 3-4 days, so repeat the misting until you've used it all up.
- - -
How it works:
Milk is a fatty colloid.
When that is exposed to sunlight, and UV, it reacts and forms a thin film that coats and protects the leaves.
It not only kills the visible mildew, but the coating goes a long way to prevent it getting a foothold again.
And the chill or Tabasco astringency helps with the PM, and is also hostile to other infection or infestation.