Burton wrote:

Hello - We're experiencing a lot of plant yellowing and we've been
told that it's due to a lack of plant nutrient, specifically nitrogen.
Our plants are well fed but could the amount of too much liquid plant
fertilizer be overwhelming the root system thereby prohibiting the
uptake of specific plant nutrients? Thank you in advance!



Have you confirmed that with a soil test? While nitrogen deficency is
probably the most common cause of yellowing, some micronutrients could
also cause that such as copper, iron, magnesium, or even a pH too high
or low.

If you have been using liquid plant fertilizer at too high a strength it
is possible that the roots could be adversely affected, limiting
nutrient takeup.

Is this in a pot or in the ground?

You could hedge your bets: (1) plant some new basil. (2) water the old
basil a lot to try to flush out excess fertilizer. (3) wait to see what
happens. If the old stuff dies, you have new stuff to replace it.