I also, too, use Morton's Kosher salt, 3lb box, for all things (I keep Leslie's iodized table salt in the shaker for others)
I took some from the bottom of the Alton Brown flippy-top glass and chrome thing that I work from, and some from the box that is +/- 4 months old. I put both samples in a glass ramekin and added some room temp water, stirred gently, waited for the cloudiness to clear and...O. M. G! clear salty water!!!! No sea monkeys.
However...It's Kosher Salt, not Kosher Sea Salt. Is there such a critter as Kosher Sea Salt? That might make a dif, I mean, if we want to go all empirical here. And I do, ackshully.
I'm almost out of Kosher Salt, and I do have to go shopping, Saturday, for Mothers Day lunch; I will take one for the team and look for Kosher Sea Salt. I will also buy a selection of the coarse sea salts offered at my local Nob Hill market, not like I won't use 'em. Oh, and a bottle of distilled water.
Then, with my vast collection of glass ramekins, which I'll run through a no-soap, high-temp wash in the dishwasher (Like I can afford an autoclave) we shall experiment and see if anything blooms. KITCHEN SCIENCE!!!!!
This'll be fun!

Kitchen science is fascinating. I doubt if there is such a thing as a salt inspector and pretty much have to take their word about what's in the box. I look forward to your report.
I was wrong about the kosher sea salt. After I started looking into it, I realized it was just the regular kosher. I found my jar of gourmet sea salt in the back of the cabinet unopened. I had been using that 3lb. box of Morton's for pretty much everything, but I put it in glass jars with screw caps lids to save space and keep out moisture. I threw the box away a long time ago.
I still want to call the company and ask them if anyone else has ever seen such a thing but they must have done away with their landlines or 800 numbers. I still have my jar of brine here with the remains. Nothing hatched though. Considering that Artemia are a part of the evaporation pond process, I don't see how they can all be filtered out plus you have the birds all around feeding and being vectors. The salt ponds down your way are a part of the migratory flyway with sanctuaries all around the ponds. After reading about all that goes into the process, I will never look at salt the same way again.