what`s happening to my crape myrtle tree shrub?

[C. A. Jr.]

hi! can any one tell me what`s the problem of my crape myrtle tree .
the  leaves are turning yellow and the tip of the leaves are somewhat
burnt. it`s been 2 1/2 months ago since i planted this tree in my yard
it`s a tall white flowering crape myrtle ( called natchez i believe).
i water it every other day since it`s kinda hot here in the south just
enough not to drown them .  it`s still blooming some flowers though
but i`m just worried  coz this yellowing leaves just happened a few
weeks ago. any advice will be appreciated. thanks!