Are you noticing leaf stippling, with chlorotic (light-colored) patches or leaves with a burnt, silvery appearance on your rhododendrons and azaleas?
Explore these links to learn how to deal with Rhododendron lace-bug, (Stephanitus rhododendri), and Azalea lace-bug (Stephanitis pyrioides):
http://www.metromastergardeners.org/files/nattersnotes/2013-5-Natter.pdf