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Dish soap forms a basic solution in water, and citric acid forms an acidic solution (obviously). By skimping on the soap and overloading on the citric acid, you're pretty much relying solely on the acid to do the cleaning, which isn't the purpose of the citric acid.
The citric acid is just to provide a nice extra shine on the tumbled brass - realistically, you could leave it out entirely and the dish soap would handle the cleaning aspect of the tumbling all by itself (assuming you used the correct amount).
A pinkish cast on brass from lost zinc isn't uncommon when you're using overly-acidic cleaners. You'll see the same thing when you use acidic quickie-cleaners like "Tarn-X" on household brass, instead of ammonia-based cleaners (which are basic, not acidic).
Try one batch with a lot more soap and a lot less acid, and see if it doesn't treat your range-darkened brass more kindly. Go ahead and give the STM recipe a try. Just for reference, the recommended 1/4 teaspoon of citric acid would be about one-fifth of a dipper full, if you're using the Lee 1cc dipper.
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