Extra NPK will not harm yr plants. But will create some algae problems. Beside that, extra NPK will not good or harm to your fishes. Extra trace element will harm to your fishes also. Which is called Metal Toxic.

Normally the fishes from lfs or farms are able to survive in the a bit higher level of NPK or a bit higher level or metal toxic. This is due to they grown in all kind of water parameter. But for sure, if anyone of them is weak or attacking by a disease. Sure die.

Try out the wild caught fishes in a tank with metal toxic and see.