basic Mirical Grow is OK to use.
I would watch for a reduction in growth OR best is to do a soil analysis & use the compound(s) indicated.....

Except for baseline soil amendments as suggested already, you should not fertilize young trees and shrubs, they will grow too vigorously. Allow the tree to mature, then once it starts fruiting, you can consider fertilizing according to annual soil analysis performed at each tree location. Soil constituency can vary greatly from one spot to the next in your yard. If you have even a gentle slope, test the soil a few feet downhill from the tree, that's where the roots are going to seek most for water and nutrients.

Even then, only fertilize and amend as REQUIRED, not as desired :))

Hey!
I must agree with scotlfs! Being too eager to fertilize fruit trees can be very counter-productive. I have found it is better to let young tree seedlings toughen up on their own for a little while. This will give you hardier trees in the long run.
Once you begin fertilizing your fruit trees, spoiled milk can be a wonderful fertilizer! I highly recommend this for outdoor trees. It is not recommended for indoor trees (for obvious reasons!).

Here is a link that might be useful: Envi Sci and Fishy Plants