I've been having the same problem for about a month ago from my first post. From my first post my Supreme Red that are housed in 20g long with CBS/CRS were dying slowly. One at a time, all signs are normal. They all eat and are active. The only shrimps that were dying was the Supreme Red not the CBS/CRS. I stopped worrying because they stopped dying.
Until recently, I ordered some Supreme Red from Nick's group buy and they were doing good for a few week. Yesterday I noticed one that was acting weird and that one die after a few hours and today I came home to a Supreme Red that was lying upside down looks dead but when I picked it up the little legs moved a little. Only the Supreme Red are dying and NOT the CBS/CRS
All these shrimps eat Shikikura, Boreno wild spinich, and grow, also along with some Hikiri shrimp cusine. I feed every 2-3 days.
Here are the water condition
Tank is Co2 injected
100% RO water, I change about 20% every 2 weeks occasionally once a week.
Kh 0 Not sure if it is zero because on the tester (tetra KH) I turned yellow color after one drop. It says that each drop is 1/2 KH. So my KH is either 1/2 or 0
No2 less than 0.3 I do not have a No3 test.
Here is a video of the shrimp that ended up dying and the PFR that is turning blueish color.
20G long Supreme Red CBS/CRS