Candles are useful when oxygen has been consumed because of respiration or a fire. They're not useful in a leak.

Conservation of mass: if a cubic meter of air escapes, that's 1.25 kg, and you need at least that much in candles. (You actually need 2 kg because the candle isn't solid oxygen)

There's ultimately 1.2 t of atmosphere on the ISS. This will also result in a pure oxygen atmosphere, which is dangerous. You need nitrogen.