Soil i'm assuming. If your fan leaves are yellowing then by all means feed it. At 30 days old they should be getting at least 400ppm of whatever nutrients you are using. The yellowing indicates to me that all the nutrients in the soil has been depleted and the plant is eating its self to stay alive.
At 30 days old they can use at least 500 ppms of nutes. Get a ppm pen and use that to figure out how much to give your plant. Also don't feed every watering either. Feed, water, water. Good Luck