After shrinking your images to 1/4 of your posted size, I did a quick but far from 100% thorough comparison of your images with the solving state in the JSudoku screen shot I posted above. They seem to be fairly identical, so the next logical step would be to carry out the eliminations from the Naked Quad on {1589} in g2:n7 => g2:r9c9 = 6.
If you get stuck again, try my above suggestion of doing a single step solving with JSudoku or SudokuSolver. They will tell you what you cannot spot.
In the above JSudoku screen shot I included all the Naked Subset eliminations upto the Naked Quad. If I count correctly, a Naked Pair is required later on.
PS:
Due to a typo grid #5 is not displayed in your above post.
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