You might try tightening the shift cable juuuust a little tiny bit. Stretching over time may mean your full pull isn't moving the derailleur cage as far as it did previously.
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A race bike in any era is a highly personal choice that at its "best" balances the requirements of fit, weight, handling, durability and cost tempered by the willingness to toss it and oneself down the pavement at considerable speed. ~Bandera