I have no idea of the site geology or your region and as usual I may not be right!
from the images it looks like high Fe soil content and the grass that has managed to escape is happy looking for somewhere else to live
start here (nothing to do with lawn and they are trying to sell fertiliser)
read the parts labeled Water logging and Toxicity Symptoms and then research from there.
EDIT: went of topic there, I agree it is buffalo and agree with CGAHS