Jonas is much more knowledgeable than me but I have some ideas until someone else can provide advice.
Get it in the shade and keep it cool as possible. Water properly, don’t let it dry out and don’t let roots sit in water. Is the soil granular and free draining? If not make sure it doesn’t stay too wet. Don’t feed 'til the tree recovers (but you may be able to apply a light dose of fish and/or seaweed emulsion). I would certainly not use a chemical fertilizer like Miracle gro, chempack, etc. at least at this time.
IMO JWP is a beautiful but touchy tree and your climate may not be the best for this this species. In nature JWP lives in the mountains where temps are cooler.
Do the best you can. Go to a bonsai club to see if you can find people that grow the species. They will probably be the best source for advice. Good luck.