Yes Speedzone Southern.
We stop applications with it when temps. get above 85 degrees high during the day. We add a little surfactant with it as well and have great results on alligator weed.
Had you applied Atrazine or Simazine to the areas in the picture? That is the effect we see after an application of either one of those products. Yellowing of the veins almost like chlorosis.
Here is a link to check out. http://plants.ifas.ufl.edu/node/33
Check out the video on the right hand side of the page. It may help you with a positive i.d.