What are your water parameters? Do they have a ton of hiding places? Sometimes putting dwarf shrimp in with a predator stresses them to the point of death if they can't hide; even if the predator is placid and ignores them.
It's a NPT and everything is at 0 (ammonia, nitrite, nitrate). I'm pretty sure it was more the stress from shipping than anything else. They do have a ton of hiding spaces (they seem to love my subswassertang) and are SUPER bright now...they were red when they arrived but now they are twice as red. :)
That's great! They are so hardy and yet so fragile. Oh, and remember, they're vulnerable when they molt so if you miss one or two they may be hiding. I thought I had lost both my Dwarf Orange Crayfish (CPOs) and then one day out they popped. I found their molts when I was doiong a surface vac.