It went dry.

Hi jean, Could it be fertilizer burn too ? The merchant sold me the plant applied a handful slow release fertilizer in the pot that day. The plant was in display room and was in a warm place. My garden is windy and dry in day time. But it's foggy at night. The maple may be in transition shock.

Hi Sam, I would say yes to your question about fert. If your merchant put slow release in the pot and you hit it with fish emulsion, i would say too much hot sauce for this little guy. Keep in mind that tree needs afternoon shade and maybe a fall pot-up. You can pot-up these at most anytime, but if you think it needs some root-work you might want to wait until dormancy.
AL

JM's also dont like very windy conditions either.

Thanks Al and Houstonetexas for their reply. I can't wait for fall to pot up. Today I unpotted the JM and it was a little pot bound. The soil mix is bark and gravel mix. I loosen up the root ball and mix some new bark along with some gravels in a 2 gallon pot. I chose not to disturb the root ball but the barks looked so old. Do you guys ever replaced the old aged barks with new barks ?

Sam, No...That partially decayed bark is the good stuff! The Garden Web also has a forum on potted trees and plants if you click on the 'other forums' link. There is some good tips on there as well, where they discuss potting medium in great detail.
~AL