These are probably Stewarsonian, a popular evergreen Gable azalea. The first three years they don't have their full hardiness and can use some winter protection. Could it be that you had snow and the tops of the plants were out of the snow and got sun and wind damage. That would account for the lack of leaves and flowers on the top. You need more sun in the summer to get more flower. My Stewartsonian is in full sun and blooms its head off every year.

I am guessing not enough sun. But, why did they bloom so well last year? Its the same amount of sun. Chicago was very dry last Summer so it may be part of it (but with new landscaping I watered like mad). Thanks for the first 3 years hardiness thoughts. It may simply be that. Ill keep it in mind. Im a believer that although nurseries recommend partial shade for certain plants, full sun is still best. At least in my area. My partial sun/shade Endless Hydragea in full sun (awesome blooms) sure supports my idea. My neighbors love them too!

Azaleas set their buds for the following Springs blooms in summer. Your azaleas bloomed after you planted them from buds set while in nursery conditions and before you purchased them.