fish emulsion is good for feeding neps and helis from what a few experts i know said but not by root feeding,but by trap feeding.
that means you pour some in the plant's pitcher.
make sure you dilute with water first!
a spray or two into the pitcher might give a try..dont over feed it
try on a nepenthes that u dont love first to see if anything bad happen.if it boost,give it a try on your beloved Neps.
Thanks
h