In general the answer is yes. Both Iris and Daylillies should have naturally begun to die down for the season. Often times seeing iris foliage dying is also an indicator that there may be iris borers in the tubers. Daylilly foliage usually dies from the older outer leaves in and those dead leaves can be removed to leave a cleaner nicer looking plant. If you have to trim back live green leaves, do the minimum that is really needed. The green leaves are still producing energy to be stored for next seasons growth, including future bloom show.
