this is some good stuff right here.Nutrients themselves don't cause algae. Your plants need macro and micro nutrients to grow. "Supposed to be providing" sounds like you are not sure exactly what type of nutrients are in your substrate and in what quantity. There is no reason you can't dose your water column too, it gives the plants two sources to draw nutrients from and helps to provide non-limiting amounts of nutrients.
Without further info about your setup i.e. tank size, lighting, photoperiod, filtration, bioload, CO2 or no CO2 it will be hard for anyone to give helpful advice.
Meanwhile here is a link to more info about the various types of algae and how to identify and prevent them.