My 3 month old ghost shrimp turned white and died over the weekend. My tank is cycled, all other inhabitants are very happy. The fish store I acquire my ghost shrimp from sell them as pets--not feeder quality. Up until this point the ghost shrimp had been very active, nothing unusual in its behavior to raise an alarm.
Searching through many forums I find this to be a very commonly described issue but solutions seem few and far between. The best lead I've found so far is that ghost shrimp turning milky is indication that the shrimp is molting as usual, however ghost shrimp need a bit of iodine in the water to help harden their new shell. About half the amount recommended on iodine products available in fish stores is supposed to be sufficient for the shrimp without irritating other tank inhabitants.
I plan on buying more ghost shrimp sometime this week and experimenting with iodine. We'll see how things pan out in 3 months. =)