I agree with you, Shoe. That one nice green healthy leaf looks good. While the milk treatment probably won't hurt, maybe look at the leaves with a magnifying glass and see if the white parts look fuzzy or not. If it is powdery or downy mildew, the leaf surface will look fuzzy.
Otherwise, I'd treat with some very dilute fert - maybe 1/4 strength of a soluble type - weekly for a couple of weeks and watch how the new growth comes along.