I'm glad you made the write up. Many other hobbyists feel isolated when it comes to shrimp deaths. Now they are able to relate a bit more with yours.
One thing I've learned while keeping shrimp is to feed very very minimally. I feed M, W, F. That's it. Extra food will decompose and cause water problem fast.
One hobbyists put it this way, "Think about feeding what you think is too little, then feed less."