Could the reddish tint possibly be weather related from cooler temp's? My first thought was maybe a type of fungal infection; a sometimes common malady for Nerium oleander is the fungal disease Xylella fastidiosa
http://www.bing.com/images/sea... but when I enlarged your photos that doesn't appear to be the case; at least it doesn't look the same to me.
At our old house I had four large Oleander trees in the yard but the only problem we had on occasion was the oleander caterpillar:
http://entnemdept.ufl.edu/crea... which defoliates the trees if you don't get them in the early stages. Hopefully someone more knowledgeable with
Oleanders (Nerium oleander) will be able to offer advice on your plants.
