Hi Tex,
For my trees, I'm using compost ( standard dirt for tomatoes seedlings ) from the nurseries and 10/10/10 "blue-bullets" for the fertilizer, a closed hand full per month - in a pot, use half of this quantity - adapt quantity to the size of the pot.
For this year, you could give one shot of fertilizer but then you need to let the tree off, for preparing the coming dormant season ...