You're not producing Co2 with candles! hahaha
CO (Carbon Monoxide) is produced with fire that emits a YELLOW flame. Such as your candle...
CO2 (Carbon Dioxide) is produced with fire that emits a blue flame. Such as a propane stove, propane lantern, or burning natural gas.
"1. BURNING HYDROCARBON FUELS:
This has been the most common method of CO2 enrichment for many years. A number of commercial growers and greenhouses use it in their larger structures. The most common fuels are propane, butane, alcohol and natural gas. Any of these fuels that burn with a blue, white or colorless flame will produce carbon dioxide, which is beneficial. If a red, orange or yellow flame is present, carbon monoxide is being generated due to incomplete combustion. Carbon monoxide is deadly to both plants and people in any but the smallest quantities. Fuels containing sulfur or sulfur compounds should not be used, as they produce by-products which are harmful."
So.... you're lucky your plants are still alive.... now blow that candle out. (did you make a wish?)