I doubt if it was the frosts. The Encore Azaleas don't have as many summer blooms in the north. They were developed in the gulf states and don't perform reliably during the summer further north. I think Virginia is out of their range for reliable summer bloom.

You might try a good azalea fertilizer next spring before they bloom. I would use Hollytone at half the rate on the package. You can also apply a phosphorus fertilizer now. I would use super phosphate at one or two tablespoons per plant.

You are right about their shallow roots. I hope you have mulched them. That is important.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

Thanx for the response and advice. It's been mulched well all along. But if they do well further south, it should have been VERY happy this summer & fall here!!!!!
It just seems so odd that it rebloomed so well the second year, and the 3rd year almost none! Do you know when they develop buds for rebloom? I was wondering if it's in the spring for summer & fall rebloom, the frost could have killed them?

Another thing to consider is the soil pH. If it's too high it could inhibit flowering. Are the azaleas in an area where lime has been applied, such as next to the lawn? A soil test sent to VA Tech will tell you if this is a problem. Your local cooperative extension office can tell you where to get the test kit. It's much more reliable than the inexpensive kits you can buy at the store.

Have you pruned them at all? I don't know when they set buds for the summer bloom but I've only done some selective pruning on mine. I'm in zone 7 near Richmond and mine bloom sporadically all summer with a full flush of blooms in spring and again in fall. I've had them for 9 years this month.

Thanx for the input! I haven't pruned, the plant is still quite small - approx. 1 foot high & wide. I had assumed the soil ph is a bit acid since all my hydrangeas nearby bloom blue. But I remember now I planted the azalea where I had a lilac previously and I had added lime to the soil then (about 9 years ago). So I'll try hollytone like rhodyman suggested & see what happens! Thanx again - Sue