What is the source of your tank water? Do you dose ferts and do you actually have a TDS meter or you got your stats from a water report? Shrimp and fish are sensitive to TDS changes which explains why some people have issues with larger water changes. The volume of water changes does not matter when the TDS remains relatively unaltered, which is the case when one uses tap water and does large water changes with the exact same source water to actually avoid TDS accumulation in the tank. Red cherry shrimp are extremely hardy in my experience but I do not keep them in fertilized tanks, which can also alter the TDS between water changes. I do large water changes, anything from 50-80% each week and I've never seen a dead shrimp due to a water change I do not know how and when they die...as I've been keeping colonies for quite some time but obviously some eventually die of old age.