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Before you touch up the edge look at it with the loup. Are there micro chips or missing spots on the edge or is it a straight clean line?

I might try doubling your stopping efforts. Do you check the edges with a loupe?

Try refreshing one or two and shave with just those razors for as long as you can.

Are you treating the razors after the shaves with any oil? If you can maintain two for longer than 8 shaves...