Certified GKH Gardening Expert
Any time that you have a plant that needs to stand in water such as these, you will have to sterilize constantly. Clean out the sauces with peroxide and then when you put them back in the saucer, you can water as normal, but replace 1/3 of that water with peroxide. This will help kill off any infection.
It might even be necessary to repot them into fresh media and then apply treatment.
This article will help:https://www.gardeningknowhow.com/houseplants/pitcher-plants/how-to-repot-pitcher-plants.htm