In my limited experience with re-blooming daylilies, they never produce as many flowers in re-bloom as in the first bloom. Also, the foliage around your daylilies has also grown over the years and may be robbing them of nutrients and water, and casting shade over them.
I once had to move several daylilies that were planted near our beloved hydrangea, because it was ribbing them of sunlight (and probably water as well.) They are flourishing in their new homes.
