My hummers giants have 2 pitchers that have some black coloring on the pitcher near the peristome. Im using the tray method with about 1/4" - 1/2" of di water. And they are under 4 2' t5ho that i got about a week ago. Are they just adjusting to their new conditions?
I've never experienced this particular problem, but if I were to hazard a guess, I would say it arose because of too much humidity with a lack of air circulation. Cephalotus appreciates high humidity, but needs good airflow.
Its not from the water level and if it was a low humidity issue the tops of the pitchers would close, like the other Ceph to the left of the hummers.
I'd need a better close-up of the black area to be of any more help. If you changed its conditions more than about 25% in any way it "may or may not" be adjusting. Pay much more attention to the new growth than the old growth if you believe this is the cause. Any fuzziness, sliminess, or other words ending in ness is likely a problem.
I'm growing many, many, many Cephs in my household humidity without any issues, they can easily be grown in 40-60%, higher humidity helps with some things but hurts others and there is already tons of threads about that disagreement.
It is pretty easy to see if you overfeed, basically can you see a large 1/4" or more area of decaying food inside the pitcher, generally around the black area. If so you probably overfeed and that individual pitcher is done for, nothing to do for it. Overfeeding can easily lead to pitcher rot.
As for what to do, let it live out its normal life cycle, once the pitcher dries up or looks like it will cause any other problems you can remove it. Provided it is just rot from overfeeding the Ceph will still benefit from leaving the overfeed pitchers attached untile they die off on there own.
I don't feed my Cephs bugs, they catch a few on there own. So hopefully someone else can chime in.
I do add fertilizers to the watering trays/flood systems/ect. Starting with 0 TDS water I add ferts to bring it up around 50/100/200 depending on the system. If your not using RO water I would be really careful with this, 50 TDS tap water is a very different animal than the 50 TDS RO water with ferts added.
I have occasionally fed pitchers with insects but not regularly. Large insects certainly would carry the risk of overwhelming the pitcher and causing decay. I don't fertilize the water, but I do add a spray or two of very dilute Neptune's Harvest (hydrolized fish fertilizer) to one pitcher once a month or so. The resulting growth has been impressive (I have a "typical" Cephalotus that rivals any of the "giants" I have seen) with no resulting pitcher rot.
I also agree with the comments to watch the new growth (which appears healthy on the plant in question) rather than the old. I always assume some period of adjustment where older leaves of a number of genera will die (I've seen this in Cephalotus and Dionaea most notably).
I would feed a pitcher like that maybe once every few months if it did not catch insects on its own. I would not feed the pitchers pictured at all. I use high protein fish food. Yes, you can, but treat it like an experiment to see if it works for you. I would soak a very small quantity, relative to the pitcher size in rainwater, then use that to feed a new pitcher.
I for one have never really feed my plants. If I remember to feed it to use a cicilid pellet food. I will put one pellet in a new pitcher and never feed that pitcher again. I do use ferts to root feed.
Honestly what I have found is when I have a lot of time to pick and poke at the plants weird things would happen and I never got the growth I wanted. When I had other distractions in life that took me away from the plants they seem to do better and grew better than before. I think some of these plants needs less of a helping hand to thrive.