Answer: I think you always take a chance when you purchase a neglected tree or shrub. It sounds as though your new little tree gave its all but simply didn't have an adequate root system to sustain growth. Flowering was probably its last hurrah. I think the fertilizer spike may have contributed to its demise. When plants are under stress the last thing they need is to be fed. Feeding forces new growth and your tree was not in any position to produce lots of top growth while it was trying to get its roots established. So, even though you did everything possible to help your tree grow big and strong, it simply did not have enough stored energy in its roots to react favorably. What a shame!
I'd replace the tree with a new one. Both fall and spring are good seasons in which to plant new landscape trees and shrubs. This is when temperatures are cooler and rainfall usually abundant, both of which will help the roots become established. Since nurseries usually get new shipments in spring rather than fall, I'd wait until then to find a healthy new cherry tree. (Although I would be tempted to visit the nursery in September to see if new trees have arrived. If so, go ahead and find a new one and plant it immediately.)
With all the TLC you gave your tree, I know you'll be successful with your new one. Enjoy!
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