Applying a heavy nitrogen based fertilizer now would definitely green your lawn up, but may not be what your lawn needs to ensure its health and appearance through the entire year. Many companies including ours are applying pre emergent control for crabgrass and liquid fertilizer that contains iron. We also treating for broadleaf weeds.
We will be applying granular fertilizer in May, June, July, and August when your lawn needs it.
Oh, back to work.