Despite Camille pointing out that this is an old thread, some may find this useful: Incomplete combustion from an open flame like a candle can produce ethylene gas. Ethylene can act as a powerful plant hormone at times, including triggering senescence. So putting lit candles near flowers you want to last for a while is not a good idea. Ripening fruit and compost piles are also sources of ethylene gas.
Ripening fruit and compost piles are also sources of ethylene gas.
Also came here to say ethylene gas from the candles seemed like a more likely suspect than heat, if related at all, and want to add that if you cook with a gas burner without proper ventilation, it can have the same effect.