Basically all plants need NPK and CO2 but not injecting CO2 and having low light generally means there is enough NPK and CO2 to keep things ticking over from fish/food waste and the CO2 already dissolved in the water. If there was none of the above then the plants would not survive. Not dosing doesn'tmean there is none in the tank but in most low light cases there is enough from natural sources to not need to dose it.
I had a Hagen Power-Glo 14w T8 in there