Asian Pear leaves Wilting and drooping. What is the problem? Please help to save my tree

I planted a 3-in-1 asian pear tree 3 months ago from bareroot.  The leaves came out ok initially, but starting 3-4weeks ago, the leaves are wilting, drooping and some turn yellow and felt off.  I am in Zone 9A.  Watering with drip about 4Gallons twice a week.  I incrased the watering the last week and doesn't seem to help it.  Is it too much water?  or is it not enough water?

potassium deficiency in plants