Azalea help

In my backyard flower bed, I planted 3 azalea bushes. 1 has been thriving for years and the other 2 have struggled due to what I think is planting them too low. I ripped the other 2 out and bought two more and planted this spring. They were doing fine until about a week ago. They went from blooming and green to literally dead as a door knob in a week. I'm at a lost. Once I saw them struggling, I watered them every other day and added a fertilizer and neither helped at all. Any ideas? This is my second set that has died but it's just so weird that the one right next to them is thriving