Sounds like it might be a combination of issues, light being one (leggy Sarracenia). Usually, when plants start out well and then decline, there are issues with the mix: possible mineral contamination, or the presence of insects attacking the roots.
If your plants are outside, then temperate dormancy will happen and is probably advisable. I would transplant everything into new fresh mix and hope for the best for next season, but if the Sarracenia are etiolating nothing short of increasing the sunlight is going to change anything in that regard.
If you know of anyone with Orthene, I would suggest that you use this systemic which will take care of many common sucking insect pests on your plants. It works very well, and has no detrimental effects to anything I have used it on, and I grow a lot of different plants.