|What would cause this slight twisting of healthy looking bearded iris leaves?
|It's probably a cultural problem - perhaps damage to the rhizome. There's a nasty disease that causes twisting of the leaves, but the symptoms include eventual yellowing of the leaves as well. Watch your iris carefully. If you see stippling or mottling of the twisted leaves your plants may have Iris Mosaic Virus. Why not dig one of the rhizomes up and look for damage? You may find insects like the Iris borers or beetle grubs, or you may find the rhizome has other physical damage which would causethe leaves to grow in a twisted way.