I was thinking about the Ro water as well--but your KH seems high enough to provide enough of a buffer--but I to am only guessing. I don't think I would use RO water for Red Cherry Shrimps as they need aged water full of the things that live in the water. RO takes them out.
The lack of babies and rapid deaths appears to me to be overfeeding. ***Before I get slammed***hear me out. Do your shrimps not show an active swarming of their food when it gets placed into the tanks? Are they lethargic and just picking at food?
Your situation sounds an aweful lot like what happened to me when I started raising shrimps. My Red Cherries were reproducing very well and all parameters were a-okay. Then I began to notice that there no babies and then my shrimps started to die off and I was left with just a few survivors in a matter of days. I found this die off phenomenon was not just happening to me but from other forums dedicated to just shrimps/inverts. A lot of shrimps keepers have lost many if not all of their shrimps due to something that appears just like this. The only explanation is that it is tied to overfeeding with all parameters testing out as 'good'. As soon as I corrected the feeding schedule and restricted myself to feeding very infrequently, my shrimps population exploded. The most difficult thing that I learned was that I could not feed the shrimps as if they were fish because they are not fish.
My shrimp have always seemed pretty active, swimming around alot more than I ever expected. Any food I placed in their tank was completely gone within a few hours. and they still graze on algae and through the substrate.
The females are heavily berried, they arent being lazy and not reproducing, the babies are either not hatching, or being eaten by something else in the tank. I found leeches living in the substrate, did some research and discovered that tiny inverts are a delicacy to them.
I caught and disposed of some sizeable leeches, apparently feasting on my cherry shrimplets. The only way I knew I could totally irradicate them was to remove the substrate where they live.
Until recently this tank was also home to 3 otos which are now living in my 20 gal yellow shrimp tank without any issues.
I have done 4 waterchanges and have gotten the ph to about 7.8 which is close to where it was I think. They seem to be stabilizing somewhat now. I have lost about half of them so far. hopefully they start to recover.
