I'm not familiar with the nutes that you're using, but when you look on the label of nutes, there's three values N-P-K, expressed as 20-10-20, and infinite variations thereof.
You want to get a nutrient with a higher first number, all else equal.
Get some GH Floragro or any other nute designed for the veg stage.
Or, ask those people telling you that your nutes are fine what you should do.
As a qualifier to this advice, the fact that you know so little about nutes makes me wonder if your diagnosis of an N deficiency is correct - either post some pics or have an experienced friend confirm that before you go buying anything else you may or may not need.