The first thing that comes to mind is that the plant is mislabeled, especially since it has a "hang on tag". The stock (Hydrangea aborescens) used for this plant does not have the genetic capability to change color. And from all I have read, white hydrangeas in general will not show color other than maybe a tinge of pink as the bloom ages.
http://www.hydrangeashydrangea...
http://www.hydrangeashydrangea... (H aborescens Annabelle was the precursor of Incrediball...Incrediball is supposed to have sturdier stems to keep flowers from drooping in the rain). On every site I looked at, the statement was made "Soil pH will not change color of the bloom"
Here is contact info for Monrovia....I would send them your pictures for confirmation.
http://www.monrovia.com/contac...
