It's up to you. That's what I would do if I had that problem, I bought a product called 'Iron Green' which is a Fe/N supplement for lawns, and I use it if there's a problem with chlorosis... but at this point in time I'm putting fish emulsion in my soil to avoid the problem to begin with... something you can't do in hydro.
If you use the veg nute, I'd say just feed once on the leaves and see if you get any improvement. You don't want to give too much N at this stage.