Here, here Steve! There is no nutrient limitation that doesn't eventually
show up as a nutrient deficiency. Nutrient limited plants must eventually
show the effect in unhealthy growth, poor coloration, loss of leaves, stunted
development and so on.
If plants are to stay healthy and robust they cannot be nutrient limited.
That doesn't mean that an aquarium has to be dosed with every chemical known
to man. The necessary nutrients can be provided through several different
pathways. It's up to the aquarist to pick a method that is appropriate to
the light and CO2 levels that they provide, the type of plants they choose to
grow and the amount of time they are willing to invest.