My preference is quarter strength MaxSea. Most of the reviews on Amazon are about how it's great for Nepenthes.
Maxsea 16-16-16 and use 1/2 teaspoon to a gallon. I just spray the leaves of the plant. I notice that pitchers die if you put it in the plant when they're young
Look into Maxsea Grow 16-16-16 1.5 Lbs. Water Soluble Seaweed Plant Food Fertilizer https://www.amazon.com/dp/B008RNTZ9O/ref=cm_sw_r_cp_api_glt_fabc_N4YTZ48HPFKDD1XR11CY
I highly record it for carnivore plants. I also believe you may have watered them too much? I may be wrong, I don’t see much perlite or sand but that’s my opinion.