watch the new growth, if it comes in greener than the old growth lower your light height if possible.
there is a misnomer out there the lots of Iron will make plants red, but thats not true, i can attest to it. high light is the best way to get good reds. that and a healthy aquarium. i would still give root tabs, or another form of ferts to help your plants stay healthy, but as long as you give good light, and keep up with water changes your plants will grow well.