ya i havent ever had one certain way a leaf folds after nute burn...but in any case if you think it is mag deficient, go buy some cal mag. folier feed... give it a week, and if it still isnt improving, then you know it was nute burn. at any rate it is always good to flush at bare minimum twice during the entire grow. once before your time switch and bloom nutes, and again 2 weeks before harvest.