I have four shrimp tanks, but for the life of me cannot figure out what's wrong with one particular tank. All my tanks are high-tech planted tanks with a mixture of ADA V1 and Stratum, and my water is extremely soft (comes out of tap around 2gh and 1-2kh add GH+ to get to between 5-6). All of them are caridina tanks (blue bolt, black galaxy pinto, CRS, and shadow black mosuras). I keep CRS in the tank I've been having issues with. This one was set up around a year ago with 10 CRS. They never really bred, but figured it was due to the way I laid out my scape since I knew there was very poor water circulation. I had to neglect the tank because a trip overseas got extended a couple months and when it came back there was a bunch of hair algae (co2 was out, but my monte carlo carpet was still green and not brown). I cleaned it out did a water change, slowly ramped up CO2 again after doing a soft rescape, I saw 2 pregnant shrimp, and decided I would help them out a bit by getting an additional 15.
They were fine at first, but after a water change 2 weeks later, despite dripping water back in I noticeably saw a huge drop in population by the third day after. Around 10 were left at the end of that debacle, but my test kit showed all the proper water parameters. I didn't even spot a single dead one even though I have an Iwagumi setup. The rest would just slowly die 1 by 1 in a span of a couple weeks until 2 left. Figured it was just due to age because these guys were abnormally big. I started having trouble with algae again, and to help added 5 amano shrimp. Drip acclimated them across 8 hours. Every week I've lost 1 shrimp including 2 of the 5 amanos I got. Usually I can spot them out because they'll look like they'll look sluggish while barely moving, but I'll see them eating and get a bit hopeful since they start swimming around.
All my other shrimps are thriving and breeding in my other tanks. Is there some slow moving bacterial infection in that one tank?