The story: I have bought a few sacks of "Plagron Royal Mix" here in Chile. This soil is supposed to be sufficient for my "tomatoes" for roughly six weeks. After four weeks in the soil I noticed problems, which seem to point to under-fertilization. Since it was time to repot anyway, the plants received roughly 50% fresh soil in a bigger pot, but the symptoms are worsening. Over-fertilization, while not impossible, seems unlikely. Before repotting, I rinsed the soil to remove excess fertilizer. (As recommended by the manufacturer)
Now considering the trip from Holland to Chile and that it's not really a hot product here, I cannot rule out that the soil was stored for a significant amount of time possibly even under adverse conditions. There are no dates on the sack.
If an organically pre-fertilized soil (peat, fibre, worm castings, etc.) is stored for a longer period of time, how does it change? Will it reduce the potency of the fertilizer? Can it have other harmful effects on plants?