Mandrew, I am not familiar with the tree but HERE is a source that I trust.

Are you truly located in FL? And this tree was fully dormant? Where did it come from? The reason I ask is that I am located in the far north (the mild far north to be sure :)) and flowering cherries have been out of dormancy here for weeks.

So describe what the tree looked like before planting and how it was wrapped or potted or whatever when you got it. The only possible reason to soak the tree roots was if it was bare rooted and the roots had dried out....which in itself is not a good thing. Longer soaking is not necessarily a help and could be a serious hindrance if the roots are already compromised.

Generally it is a planting soil that is specified for trees and shrubs, not a potting soil and there is a significant difference between the two. If you are growing it in a container or pot, you want to use potting soil. And a good quality, longlasting, high durability mix at that, like Al's gritty mix you'll find referred to frequently here. If you are growing it in the ground, you can amend the area with the planting soil, although that is not always a requirement or even advised in many cases.

If planted in a container, fertilizing is a must, whether you start out with a slow release like Osmocote to begin with or just use a liquid. Plants that go directly into the ground are generally NOT fertilized at planting although a starter or root boosting fertilizer can be used.

Will any of these issues kill the tree? Doubtful :-) Good drainage is the most important issue when dealing with a containerized tree......after that, providing sufficient water and nutrient supplementation. Coffee grounds are a weak fertilizer at best and not much use in a container situation. Much better to add them to a compost, then add to the garden. They can be used as a mulch but if allowed to dry they will crust over and become water repellant.