Simply put, it is all about the soil composition. The Guion side of the forest tends to be more of a sandy loam soil, while the higher elevations have more clay. Sandy loam drains well, while clay does not allow water to peculate. Muddy conditions are the worst I have ever seen in DSF for this time of year, the daily rains are the culprit.
Clay trail tread is susceptible to minor soil loss during heavy rain events, and then this soil settles in the dips or wherever the water slows down. Even well designed and built trails need some work, many of these trails need de-berming and increased outslope in the areas of dips. Horse traffic on these trails can also make problems worse, as they tend to loosen soil (displacement forces) when they travel and when the mud build up begins the pock macking makes it very hard for the water to escape the teacups.
Airstrip and Laurel Ridge have a number of muddy areas, I rode these yesterday and they are worse than I have seen for this time of year (winter mud is to be expected with freeze/thaw cycles).