Oh boy, did you buy a store brand bag of peat moss? Some may not be even sphagnum moss at all, just processed humus. Or if it is sphagnum peat moss, some have additives like wetting agent or fertilizer added to it. In both case, that is deadly to CP.

Did you read the bag of peat moss if what you are using has additives? Peat moss for CP should not contain fertilizer or wetting additives at all. It must be pure sphagnum peat moss.

I strongly recommend you repot them quickly and make sure you read the bales of peat moss that it doesn't contains additives, and make sure it says sphagnum peat moss and nothing else.

I purchased the bale last season from an independent nursery that mostly distributes wholesale plants.

It appears to not be --100%-- sphagnum as there are some twigs in it. But the package does say "sphagnum" peat. I would think it would also advertise on the label "pH balanced" or "with wetting agents" if that was the case. Then again, I can't explain why the runnoff is pH neutral if the medium is significantly acidic.

Since I potted the plants last Thursday, there is new growth on one of the two large (unidentified) rhizomes and the Sarracenia rubra alabamensis ... but nothing else.

I'll have time to repot them Friday ...

I would buy LFS, the long fibered sphagnum, for $4, at Home Depot or Lowes. Can't go wrong there.

Mine tests at very acidic, very low ppm, and very low nitrites and nitrates. I bought my moss and perlite at Sarracenia Northwest and just used a generic aquarium test kit for fresh water.

I would suspect that high pH sphagnum is either treated or not true sphagnum. Anything in small bags is sually fertilized. The big, square, 2X2 bales of pure sphagnum in plastic wrap are usually untreated. Also, check your sand. If it is not silica sand, it might harm your plants too.