What is the best way to get a dieing young tree life again? Nutrients?

Not sure why it is dying, but I found a site that hopefully helps: https://brightnest.com/todos/save-a-dying-plant

Take soil sample into farm feed mill or some garden centers can test soil for lost nutrients as to why it's sick look on lung Google your plant tree bush and ask why its not doing well or decribe what you see it may be a moth or bug

On line ( not lung) Internet

Last and maybe first resort for any plant is to use FISH EMULSION .

First before the question should be answer....what type of tree and w=exactly what is going on with it?

It could be something in the soil that is missing from the needed nutrients or an infestation, look the tree over carefully for any activity by insects or fungus. You might want to get the soil tested.

We had a similar problem with Rosemary in this certain pot, it just up and died, we could see nothing wrong. Next year we planted another Rosemary plant in the same pot, it died too, chalked it up to something in the soil that was toxic to it.

Thankyou very much!