Ann, a picture would help us a lot. Mottled look sometimes indicates sucking insects like spider mites, but my azaleas never seem to suffer from spider mites. (and I have lots!)
If you could take a magnifying glass and look closely at the speckles underneath the leaves, to see if they are insects or fungus that would be a good clue. Better yet, post a picture.
For insects, a solution of soapy water should help. 1/2tsp. dish soap per quart of water in a sprayer bottle, or if you have a gallon sized pump sprayer (better for a big bush) 2tsp. per gallon. Be sure to spray all surfaces of the leaves, and the stems. Repeat after it rains, and at least a couple of times per week for a few weeks, as new babies will hatch even if you've killed their parents.
For fungus, a solution of baking soda/water is a preventative. It won' t make what is now there go away, but will stop the spread. Again it is 1/2 tsp. baking soda per quart of water. Here's a good link to treatment if what you have is indeed Azalea Rust Fungus
http://www.ehow.com/how_867117...
