See attachment s

Not a "blight."  It's known as physiological leaf scorch and is commonly associated with an inability of the tree to provide sufficient water to the leaf cells to keep them alive.  It's why the necrosis occurs at the tips of the leaves the furthest away from the roots.

It's a common problem with Japanese maples.  They will not tolerate moisture extremes at either end of the spectrum:  too much water is just as bad as too little.  Too much water causes the roots to shut down.  If it goes on too long, they can die.  Of course, too little means additional watering is required; however, the key is to check the soil moisture before watering!  The main point is to avoid "roller-coaster" soil moisture levels.

A couple of things to consider.  Does the downspot in the picture drain onto the root area of the tree?  If so, you should re-direct it away from the tree.  Second, you may want to consider replacing the stone around the tree with hardwood bark mulch.  The mulch will help to regulate soil moisture and will keep the root zone cool; two things the stone will not do.