I looked at the pictures, and can tell that they are streaks. But to tell what those streaks are, you'll have to take MUCH higher resolution pictures.
However, if you hosed off uncured plaster, odds are that the streaks are IN the plaster. In that case, I'm not sure of anything that would remove them, except possibly grinding down the plaster some. Acid washing will actually tend to remove washed out places more than unwashed (and smoother) areas, and could even make the streaks more promininent.
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