i got my first marm from aquabid as well!
from my observations..i've seen a berried marms eggs "dissappear", with no indication of recruitment, in the one that i did notice this happen, the eggs seemed to be more "grayish" in color than other berried marms i've inspected.. most of the time, the young copies of the mother will stay with the her for at least a day or two, i suspect that the eggs weren't viable but don't know for sure
i've only seen them go into berry after molting..(was it shipped to you in berry?)
i've lost a few, and from what i found i suspect that they died either during the molt or right after (all losses so far have exhibited very soft shells)
so after more online research i went and bought some marine aquarium iodide.. it's recommended that you use half the dosage recommended for salt water tanks... since i started using the iodide i've only found 2 dead, one i think was from a fight in a breeder tank (first and only time i've seen that!) and was partially canablized, the other was a floater in the pool that i have no idea how it died,,, it had been dead for a while

anyways,, i hope this helps!

oh, one more thing.. i haven't seen this yet, but if you ever notice a marm with what looks like a "tumor", try to segregate it and observe.. when it molts the "tumor" is really another marm!