Armadillidium Werneri care?

[Acro 23]

I had a good sized group of Armadillidium Werneri, about 30 or so.  I kept them just like my Armadillidium klugii 'slano' and Armadillidium nasatum 'peach' (ventilated container, half substrate dry, half moist, same foods, etc.).  I had them for about 8 months, and somewhere in that time, then they just started dying.  It was about 1 to 3 a month that would die.  They didn't seem to be reproducing, and all I was left with was a beautiful group of a few adults.  I ended up sending those survivors to a friend to see if he had better luck.

Now that they are gone . . . I've been thinking about keeping them again. 

So with the back story out of the way, what might I have done wrong and how should I care for them in the future?