Yep, that's the trouble with shipped eggs. You don't know how long they have been collected, how they have gone through the shipping/handling process (x-rayed, shaken, thrown around) sometimes 1 hatches, sometimes all and sometimes none. It's just a toss up.
Then theres the incubation process where so many things can and will influence the hatch rate.
I order eggs every once in awhile (mainly pheasant eggs) and usually have pretty good results. You also have to take in consideration that some breeds/species have low fertility rates to begin with....this is especially true with pheasants.
Congrats on your 2 that did hatch, nice looking chicks.