Macro Nutrient Deficiency


>Dupla stuff is not equivalent to providing all the right nutrients. There
>are both micro nutrients and MACRO nutrients.  All plants must have both -
>and once they run out of one element they will start to recyle from the
>older leaves.
>This may be more apparent in the HEAVY feeders, like sword plants. 
>In tanks with light fish load, running out of MACRO nutrients can be a real
>problem. With regular water changes (and certain water supplies), macro
>nutrients might be replenished. But sometimes they need to be supplemented.
>Conceivably, this can also apply to P and K, in addition to N. Other
>essential nutrients include Ca, S sometimes not included with nutrient
>I have added Sodium Nitrate directly to tanks with sword plants that were
>doing poorly, and growth then picks up.  (But of course, lighting must also
>be sufficient).

Anybody know of specific symptoms or signs to look for when suspecting macro nutrient deficiency?