Toss in floaters temporarily.
Seems to help.
I wouldn't worry too much unless something is really wrong with your water.
Obviously you don't want any losses but I have noticed that if the water is a little bit bad it will just sort of thin the herd - there seems to be a big difference between the hardiest of the shrimp and the weakest. You get a few deaths and think "oh no, they are all going to die" but they usually don't.