Easy fix for this... add 2 tablespoons of lemon juice to each gallon of water before tumbling. It also makes the brass shine!
Other "pearls" I've had explained to me or have learned on my own...
1. Don't reload or cast when distracted. Distractions are very bad.
2. If you have lubed boolits that you're going to re-cast.... clean the lube off before putting them back in the pot. Don't do what I did and get visited by the tinsel fairy.
3. Wear a face mask when casting. Full face shields are cheap, eyes are expensive and they don't grow back.