Pitch starter for infection?

I brewed a Hefeweizen with an OG of 1.050 & it stopped fermenting @ 1.019.
It seems to have a slight sour taste to it & not much banana as I can tell.
Anyhow, I did not use a yeast starter on this 5 gal. batch & I fermented @ 70 deg. using WLP300 yeast.
My question is if I were to put the beer into a secondary & pitch a fresh yeast starter, would this possibly kill or mask any sourness?

Cheers!

5 1/2 gallon batch
7.75 lbs. Wheat Malt
4.25 lbs. Pilsner
154 F Mash @ 60 min.
90 min. Boil
WLP300 Hefeweizen yeast (no starter)
Ferment @ 70 deg.

The sour will not go away if it's an infection. That yeast is known to have low attenuation. Is it just green or do you think it is actually infected?