LenG444,
Aside from the posibility that the peat or perlite had fertilizer mixed in them, there is also the possibility/probability that the plants were more susceptible to mold problems because of the the several changes they went through getting to you. First they are unpotted and the soil cleaned off, then stuck in a dark container and banged around for several days, then stuck in a new soil mix, in a new environment. That's a lot to take for anybody.
On a another note, and I stress I don't know if this is what you had, but while Schultz tends to be a good brand, I had to throw out 5 bags of their peat moss late last season because they were so badly contaminated with a yellowish mold. These bags were opened directly after getting them home from the store.