We have 3 azaleas first planted 8 years ago. Moved all three about 3 years ago and all have flowered until this year. All planted in same area of about 8 x 8 feet. One azalea has its usual fantastic display of flowers, the other two have about 4 to 5 flowers only. They otherwise look very healthy and foliage is fine. We moved them from a flat area to a more sloping area. It is the one furthest down the slope that has flowered well. We live on the Isle of Man.
Azalea Not Flowered
Certified GKH Gardening Expert
It sounds as though the plant is lacking phosphorus. This would cause the plant to stop blooming. Add some phosphorus to the soil. This article will help: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm