I have never seen anything like this happen to nepenthes but one of my fern exhibit the same symtoms some time back. I check with my local nursery and they told me it's caused by some kind of mineral or something deficiency and to just give it a small amount of organic fertelizer. I did as told and my fern did recover after that.
Disclaimer: The author will not be responsible for any loss or damage if the said method does not work for nepenthes. No claims for compensation will be entertain
