Just leave it alone and ensure it is adequately watered. There's nothing you can do to make it grow any fasted. Apart from that it would be better off planted in the ground. Is that not possible?

where are you. and what shocked it into losing all its leaves???

frost.. freeze .... ????

many plants can releaf multiple times ...

no more fert ... its not a child ... and not hungry .. and most likely ..... the grower put enough fert in that pot for 2 or 3 years ...

and i agree.. get it in the ground ...

ken

i also note.. the clump of old media that defines the prior small pot .... just jammed in a larger pot .... i suspect severe root circling ... you may want to completely bare root the plant .. and fix the root issues at planting.. but not knowing where you are .. i dont know when that should be done.. you may need to stick it in the ground. and do the root surgery in fall ..

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

Plant it in the ground, water thoroughly.