The photo is not clear enough to determine the problem. There looks to be some dieback and the growth is not very lush but other than that, I'd just be guessing without something more visible to substantiate the "bad shape".

I will tell you that JM's can often have delayed reactions to stress - like the big temperature swing as they were leafing out - and that certainly could have affected how well the tree leafed out this season. Exposure to stress can also lead to some rather more severe disease issues although on the surface that doesn't look like the case here. But cultivation in the root zone (i.e. moving/dividing the hostas) should be avoided and make sure the tree is getting adequate (but not excessive) water. At this time in the season there is not much else you can do except hope for the best and that the tree leafs out more fully next season.