The constraint
Dust and Glow was already working. That makes the constraint harder to see, because nothing looks broken.
The limit was how fast fresh concepts reached the account. Creative fatigues at the rate you spend against it, so a working account with a thin pipeline will hold CPA right up until it does not, and then the whole curve moves at once.
The outcome
Spend went from $8,625 to $18,074, a 2.1× increase, while CPA moved from $38.85 to $38.54. Flat, inside noise.
The honest read: this is a scaling result, not a turnaround. The account was healthy before we doubled it. What we added was enough concept volume that the extra budget had somewhere new to go.
The creative
The ads that produced those numbers, exactly as they ran.
Creative fatigues at the rate you spend against it.
Doubling budget halves the life of everything in market. The pipeline has to double with it, or CPA collects the difference a month later.