hmmm well i think it is your acclimation method, i drip acclimate everything for one hour before it goes in my tank sometimes longer it sounds rediculous yes but i havnt had one death yet (knock on wood) i have 2 shrimps plan on getting more... but many people go into this not knowing how important acclimation is its one of the most important steps in this hobby, by acclimating slowly you reduce the stress level alot and it feels more comfortabl whatever IT is, and it helps reduce chance of desease alot.... you should read some articles on drip acclimation its very easy and simple, and if that isnt it when you do water changes your salinity might be changing too sudden try to get it the same as the tank and if its off only 0.001 at the most .... but i doubt its that.