It is normal for Lady ferns to go dormant at this time of the year. If the weather has been very warm and dry, that may have advanced the dormancy a few days or weeks.
Lady ferns, Japanese Painted ferns and their hybrid, the 'Ghost' ferns, require a shady location and consistently moist soil for best performance.
A large colony, as you have, is ample evidence that they are perfectly happy in that location and will return next spring. No worries!
Rb

Lady fern is actually a prolifically self-spreading almost nuisance plant whose well-being you probably don't need to worry about. In my climate they sow themselves into every conceivable condition, not just moist shade, though obviously mostly there. You may have more concerns about controlling them than about preserving them!

KarinL