Water Hyacinth

[DrOizo]

In my 4 week old 33 gal pond with two Comets, oxygenating weed, water hyacinth and two minature lillies, the leaves on the hyacinth are looking yellowy. I assume this is an nitrogen, potassium or phospate defficency in the water but Should I fertilise? the pond is in its algal bloom stage but won't fertiliser stimulate the algae and lead to an algal bloom?
What should I do to save the hyacinth
Cheers