What's your question? Ask

unless you provide the exact environment that it needs, it will start to deteriorate very fast.

There are about as many reasons for this to happen as their are species of these plants.

The good news is that the one you have appears to be one of the more forgiving of the genus.

Things that can cause this are many and include nutrients into eh soil mix around the root zone, underwstering, putting the plant un any soil at all (they require a soilless mix of sphagnum and perlite since it contains no nutrients that will burn the roots. These plants feed solely through the insects they consume.

Other reasons include low humidity, sitting in stagnant water, too much light, disease, insect damage, chemical burn, bird droppings in the plant or on the soilless mix, and low temperatures.

You have quite the long list of problems to rule out, but this species will be most tolerant of some of those conditions being less than perfect.

This will offer more information on their care but keep in mind that you never fertilize the soil. You fertilize when it cant get insects by spraying with a quarter strength orchid fertilizer on its leaves:https://www.gardeningknowhow.com/houseplants/pitcher-plants/growing-pitcher-plants.htm