Spots on plan

I have two plants that are 3 weeks old now from a clone. I noticed today that one of the plants is starting to get white/faded spots on it. They're being watered twice a day for 1/2 hr each time and for nutrients they're currently at ~ 5/1/3.

I haven't checked the ph of the water in about 3 days but it was 6.4. This is only happening to one plant

looks like mold or what they call powdery mildew

never had it don't know the fix but you can search it