Ok first off, you need to get your water params. With fish you can get away with a wide range of params usually but shrimp no! Thy have to have a high enough ph and calcium content or there exoskeleton will dissolve or they will not be able to recover from a molt. Also I assume you dont have any fish so you probably ok there but if the tank is new and you are sure the bacteria is there then add shrimp slower. Like maybe 6 at a time. Then feed them algae wafers, shrimp pelets, or even blanched veggies.
Hope this helps. I had AWFUL experience with my fish at first. Get the params checked and ask them to check kh and gh. Make sure it is high enough for the shrimp. I am not sure what is high enough as its kind of confusing to me but my lfs said I was low and that the one that adds calcium was virtually nonexistant. I added aragonate to the filter and voila problem solved! God bless and happhy fish...er...shrimp keeping!!!