Great experiment you're conducting here tzestan and thanks for sharing your findings.
However for me (and me only), IMHO manually feeding the pitcher to see how it would help / benefit the nep is a redundant experiment. We all know most nep will grow better if nutrients were available to the plants via pitcher absorption. For most of us, most nep are more than capable of catching their own "food" when grown outdoor in our tropical weather. Personally, to experiment the advantages of fertilizing via root zone and applying it via foliar spray is a more interesting subject since there's really a lack of results (I can only find a few on internet) to show whether it'll greatly benefit the nep and
most importantly, how to properly do it to get the intended results...
Yet, it's still interesing to see if what you're trying to find can significantly imporve the growth of neps. As he saying goes....
"Never try, never know..."
. Please keep us updated...